Plaintiff-appellant, James Gaylord, appeals a judgment of the trial court upholding Gaylord's *288discharge from employment as a high school teacher by defendant school district. A prior appeal resulted in a remand to the trial court to enter new findings based upon application of the proper statutory burden of proof of the district. Gaylord v. Tacoma School Dist. 10, 85 Wn.2d 348, 535 P.2d 804 (1975). The case now before us is an appeal from the judgment entered on new findings and conclusions entered by the trial court on remand.
Defendant school district discharged Gaylord — who held a teacher's certificate — from his teaching position at the Wilson High School in Tacoma on the ground of "immorality" because he was a known homosexual. Gaylord appealed this decision to the Superior Court for de novo trial under RCW 28A.88.015. The court after trial entered findings, conclusions, and judgment to the effect there was sufficient cause for discharge. Gaylord then appealed the Superior Court judgment to this court which in turn remanded the cause back to the Superior Court for further consideration. It had erroneously construed a statute to require it to give special weight to the testimony of school personnel. Gaylord v. Tacoma School Dist. 10, supra. On remand reconsideration, the Superior Court concluded in substance Gaylord was properly discharged for immorality because he was homosexual, and as a known homosexual, his ability and fitness to teach was impaired with resulting injury to the school. Gaylord again appeals to this court assigning error to various findings, conclusions, and judgment.
We need consider only the assignments of error which raise two basic issues: (1) whether substantial evidence supports the trial court's conclusion plaintiff-appellant Gaylord was guilty of immorality; (2) whether substantial evidence supports the findings, that as a known homosexual, Gaylord's fitness as a teacher was impaired to the injury of the Wilson High School, justifying his discharge by the defendant school district's board of directors. The relevant findings of the trial court may be summarized as follows.
*289Gaylord knew of his homosexuality for 20 years prior to his trial, actively sought homosexual company for the past several years, and participated in homosexual acts. He knew his status as a homosexual, if known, would jeopardize his employment, damage his reputation, and hurt his parents.
Gaylord's school superior first became aware of his sexual status on October 24, 1972, when a former Wilson High student told the school's vice-principal he thought Gaylord was a homosexual. The vice-principal confronted Gaylord at his home that same day with a written copy of the student's statement. Gaylord admitted he was a homosexual and attempted unsuccessfully to have the vice-principal drop the matter.
On November 21,1972, Gaylord was notified the board of directors of the Tacoma School Board had found probable cause for his discharge due to his status as a publicly known homosexual. This status was contrary to school district policy No. 4119(5), which provides for discharge of school employees for "immorality." After hearing, the defendant board of directors discharged Gaylord effective December 21,1972.
The court found an admission of homosexuality connotes illegal as well as immoral acts, because "sexual gratification with a member of one's own sex is implicit in the term 'homosexual.'" These acts were proscribed by RCW 9.79-.120 (lewdness) and RCW 9.79.100 (sodomy).
After Gaylord's homosexual status became publicly known, it would and did impair his teaching efficiency. A teacher's efficiency is determined by his relationship with his students, their parents, the school administration, and fellow teachers. If Gaylord had not been discharged after he became known as a homosexual, the result would be fear, confusion, suspicion, parental concern, and pressure on the administration by students, parents, and other teachers.
The court concluded "appellant was properly discharged by respondent upon a charge of immorality upon his *290admission and disclosure that he was a homosexual" and that relief sought should be denied.
Was Gaylord guilty of immorality?
Our concern here is with the meaning of immorality in the sense intended by school board policy No. 4119(5). School boards have broad management powers. RCW 28A-.58. Under RCW 28A.58.100(1) the school board may discharge teachers for "sufficient cause." Policy No. 4119(5) adopted by the school board and in effect during the term of Gaylord's teaching contract with defendant school district permits the Tacoma School Board of Directors to treat "immorality" as sufficient cause for discharge.
"Immorality" as used in policy No. 4119(5) does not stand alone. RCW 28A.67.110 makes it the duty of all teachers to "endeavor to impress on the minds of their pupils the principles of morality, truth, justice, temperance, humanity and patriotism ..." RCW 28A.70.140 requires an applicant for a teacher's certificate be "a person of good moral character." RCW 28A.70.160 makes "immorality" a ground for revoking a teacher's certificate. Other grounds include the commission of "crime against the law of the state." The moral conduct of a teacher is relevant to a consideration of that person's fitness or ability to function adequately as a teacher of the students he is expected to teach — in this case high school students. See Morrison v. State Bd. of Educ., 1 Cal. 3d 214, 225, 461 P.2d 375, 82 Cal. Rptr. 175 (1969).
"Immorality" as a ground of teacher discharge would be unconstitutionally vague if not coupled with resulting actual or prospective adverse performance as a teacher. Denton v. South Kitsap School Dist. 402, 10 Wn. App. 69, 516 P.2d 1080 (1973); Morrison v. State Bd. of Educ., supra at 225 n.15. The basic statute permitting discharge for "sufficient cause" (RCW 28A.58.100(1)) has been construed to require the cause must adversely affect the teacher's performance before it can be invoked as a ground for discharge. Gaylord v. Tacoma School Dist. 10, supra.
*291It follows the term "immorality" is not to be construed in its abstract sense apart from its effect upon teaching efficiency or fitness to teach. In its abstract sense the term is not and perhaps cannot be comprehensively defined although it can be illustrated.
When, as in the case here, the term "immorality" has not been defined in policy No. 4119(5), it would seem reasonable to give the term its ordinary, common, everyday meaning as we would when construing an undefined term in a statute. New York Life Ins. Co. v. Jones, 86 Wn.2d 44, 47, 541 P.2d 989 (1975); State v. Jones, 84 Wn.2d 823, 830, 529 P.2d 1040 (1974); Glaspey & Sons, Inc. v. Conrad, 83 Wn.2d 707, 711, 521 P.2d 1173 (1974).
Was homosexuality immoral within the meaning of policy No. 4119(5)? We must first examine what the much dicussed term "homosexuality" means. In J. Walinder, Transsexualism 3 (1967), the author approves the following statement:
The crucial characteristic of the homosexual is the desire for a physical sex relation with a person of his own sex. The eonist is repelled by the physical aspect of a homosexual relationship. (2) Homosexuals do not want to change their sex and identity. This is the fundamental anomoly [sic] in eonism.
D. West, in Homosexuality 10-11 (1967), the author explains:
Homosexuality simply means the experience of being erotically attracted to a member of the same sex, and men or women who habitually experience strong feelings of this kind are called homosexuals. Those who act upon such feelings by participating in mutual sexual fondling or other forms of sexual stimulation with a partner of the same sex are known as 'overt' or practicing homosexuals. Those whose erotic feelings for the opposite sex are absent altogether, or slight in comparison to their homosexual feelings, are called exclusive or obligatory homosexuals. This is the type doctors usually have in mind when they refer without further qualification to 'homosexuals', or when they speak of 'true' homosexuals or "inverts", or when they consider the condition more or *292less permanent and unchangeable. Indeed, it is this exclusive, obligatory type of homosexual who presents the chief problem for contemporary society, and who is the main concern of this book. The thought of intimate contacts with their own sex disgusts many normal persons, but many of these exclusive homosexuals, especially male homosexuals, are even more appalled by the prospect of relations with the opposite sex.
(Footnote omitted.)
In characterizing homosexuality as immoral, the New Catholic Encyclopedia, for example, defines the term homosexual as:
[AJnyone who is erotically attracted to a notable degree toward persons of his or her own sex and who engages, or is psychologically disposed to engage, in sexual activity prompted by this attraction.
. . . Once friendship between persons of the same sex leads, to physical expression, a homosexual act has occurred . . . The danger remains that the individual will yield to desire for the overt act.
7 New Catholic Encyclopedia 116 (1967).
Other observations and definitions of homosexuality are in substance similar to those above quoted. See H. English & A. English, A Comprehensive Dictionary of Psychological and Psychoanalytical Terms (1958); H. Eysenk & W. Wurzburg, Encyclopedia of Psychology 66-67 (1958); 1 R. Goldenson, The Encyclopedia of Human Behavior 553-59 (1970); Blackison's New Gould Medical Dictionary 471 (1st ed. 1949); Dorland's Illustrated Medical Dictionary 686 (24th ed. 1965); Psychiatric Dictionary 348-51 (4th ed. 1970); Steadman's Medical Dictionary 584 (22d ed. 1972). See generally The Encyclopedia Americana 629 (1963); 16 Encyclopedia Britannica 603 (1974); 14 International Encyclopedia of the Social Sciences 222 (1968).
There appears to be general agreement, so far as it goes, with Webster's definition of homosexual: "'one whose sexual inclination is toward those of the individual's own sex rather than the opposite sex.'" State v. Rose, 62 *293Wn.2d 309, 313, 382 P.2d 513 (1963). In State v. Rose, supra at 313, the court approved this definition, continuing
As thus defined, its application in describing appellant might be a permissible deduction from the evidence when arguing to the jury.
The medical and psychological and psychiatric literature on the subject of homosexuality distinguishes between the overt homosexual and the passive or latent homosexual. An overt homosexual has homosexual inclinations consciously experienced and expressed in actual homosexual behavior as opposed to latent. A latent homosexual is one who has "an erotic inclination toward members of the same sex, not consciously experienced or expressed in overt action; opposite of overt." Steadman's Medical Dictionary, supra at 584. However, it has been pointed out that "[ajctually, individual homosexuals do not necessarily maintain an active or passive attitude exclusively in a given relationship, inasmuch as they alternate in the male and female roles." 3 A. Deutsch & H. Fishman, The Encyclopedia of Mental Health 747 (1963).
Moreover, homosexual experience of an overt nature varies among homosexuals, from males who are more or less exclusively homosexual to males that are only occasionally so. See A. Kinsey, W. Pomeroy & C. Martin, Sexual Behavior in the Human Male 650-51 (1948). See generally C. Socarides, The Overt Homosexual (1968); 3 American Handbook of Psychiatry (2d ed. 1974).
In the instant case Gaylord "admitted his status as a homosexual" (finding of fact No. 5) and "from appellant's own testimony it is unquestioned that homosexual acts were participated in by him, although there was no evidence of any overt act having been committed." (Finding of fact No. 3.)
These findings concerning Gaylord's homosexuality are based both on his admission and on other evidence. In determining the significance of the admission we first note the related rule stated in 2 C. Moore, A Treatise on Facts or the Weight and Value of Evidence § 1178, at 1322 *294(1908): "If the meaning of a party's written statement is in doubt, that construction must be adopted which is least favorable to him; 'he selected its language.'" (Citing Wood v. Chetwood, 44 N.J. Eq. 64, 14 A. 21, 24 (1888).) This court has also adopted the rule that ambiguous language in written instruments "should be construed against the party using the language." Jacoby v. Grays Harbor Chair & Mfg. Co., 77 Wn.2d 911, 918, 468 P.2d 666 (1970); Wilkins v. Grays Harbor Community Hosp., 71 Wn.2d 178, 427 P.2d 716 (1967).
This rule of construction concerning his admission of homosexuality is supported by evidence that Gaylord was and had been a homosexual for 20 years. He also testified that in the 2-year period before his discharge, he actively sought out the company of other male homosexuals and participated actively as a member of the Dorian Society (a society of homosexuals). He responded to a blind advertisement in the society's paper for homosexual company. He concealed his homosexuality from his parents until compelled to reveal it by the present dispute.
If Gaylord meant something other than homosexual in the usual sense, he failed to explain what he meant by his admission of homosexuality or being a homosexual so as to avoid any adverse inference, although he had adequate opportunity at trial to do so. He clearly had a right to explain that he was not an overt homosexual and did not engage in the conduct the court ascribed to him which the court found immoral and illegal. Evidence that explains the admission or qualifies it is clearly admissible. 1 Conrad, Modern Trial Evidence 377 (1966). See National Ass'n of Creditors v. Grassley, 159 Wash. 185, 292 P. 416 (1930); Ryan v. Westgard, 12 Wn. App. 500, 530 P.2d 687 (1975); Berkovitch v. Luketa, 49 Wn.2d 433, 302 P.2d 211 (1963). There was uncontroverted evidence plaintiff was a competent and intelligent teacher so the court could reasonably assume Gaylord knew what homosexuality could mean. It was not a word to be thoughtlessly or lightly used. Gaylord's precaution for 20 years to keep his status of being *295a homosexual secret from his parents is eloquent evidence of his knowledge of the serious consequences attendant upon an undefined admission of homosexuality.
He testified that in June 1970 he realized that if he was "ever going to have [homosexual] friends . . . that I needed, that I was going to have to make more efforts of my own to find these people because I wasn't going to stumble across them by accident as I expected." It was about that time he joined the Dorian Society. He testified he "felt very comfortable with the people there." Eventually he began to attend a good many of their functions. On one occasion a high school boy conferred with the plaintiff about homosexuality and learned that plaintiff was "heavily involved" for a period of a month with a person whose advertisement he had answered. It would have been a simple matter for Gaylord to have explained the physical side, if any, of his relationship but he did not do so.
Our next inquiry is whether homosexuality as commonly understood is considered immoral. Homosexuality is widely condemned as immoral and was so condemned as immoral during biblical times. A. Kinsey, W. Pomeroy & C. Martin, Sexual Behavior in the Human Male 483 (1948); S. Weinberg & C. Williams, Male Homosexuals 17-18, 252, 256 (1974); D. West, supra at 96-101; 8 Encyclopedia Judaica (1971) col. 961; 7 New Catholic Encyclopedia 116-19 (1967); 3 A. Deutsch & H. Fishman, The Encyclopedia of Mental Health 763 (1963).
A sociologist testified in the instant case: "A majority of people and adults in this country react negatively to homosexuality." A psychiatrist testified "I would say in our present culture and certainly, in the last few hundred years in Western Europe and in America this [homosexuality] has been a frightening idea ..."
'The court found "sexual gratification with a member of one's own sex is implicit in the term 'homosexual.'" (Finding of fact No. 8.) This finding would not necessarily apply to latent homosexuals, however, the court in effect found from the evidence and reasonable inferences therefrom, it *296applied to Gaylord. These acts — sodomy and lewdness— were crimes during the period of Gaylord's employment and at the time of his discharge. RCW 9.79.100 and RCW 9.79.120.
Volitional choice is an essential element of morality. One who has a disease, for example, cannot be held morally responsible for his condition. Homosexuality is not a disease, however. Gaylord's witness, a psychiatrist, testified on cross-examination that homosexuality except in a case of hormonal or congenital defect (not shown to be present here) is not inborn. Most homosexuals have a "psychological or acquired orientation." Only recently the Board of the American Psychiatric Association has stated: "homosexuality .. . by itself does not necessarily constitute a psychiatric disorder." The board explained that the new diagnostic category of sexual orientation disturbance applies to:
"individuals whose sexual interests are directed primarily towards people of the same sex and who are either disturbed by, in conflict with, or wish to change their sexual orientation." . . . [this is] "distinguished from homosexuality, which by itself does not necessarily constitute a psychiatric disorder."
A.P.A. Rules Homosexuality Not Necessarily a Disorder, 9 Psychiatric News (Jan. 1974), at 1.
Nevertheless it is a disorder for those who wish to change their homosexuality which is acquired after birth. In the instant case plaintiff desired no change and has sought no psychiatric help because he feels comfortable with his homosexuality. He has made a voluntary choice for which he must be held morally responsible. L. Hatterer, Changing Homosexuality in the Male, Treatment for Men Troubled by Homosexuality 58, 445 app. 1 (1970).
The remaining question on this point is whether the repeal of the sodomy statute (RCW 9.79.100), while this case was pending, deprives sodomy of its immoral character. In the first place the repeal did not go into effect until July 1, 1976, sometime after Gaylord's discharge. Sodomy between consenting adults is no longer a crime. RCW *2979A.88; RCW 9A.98.010; RCW 9A.88.100. See also RCW 9A.88.010 and .020. Generally the fact that sodomy is not a crime no more relieves the conduct of its immoral status than would consent to the crime of incest.
The next question is whether the plaintiff's performance as a teacher was sufficiently impaired by his known homosexuality to be the basis for discharge. The court found that Gaylord, prior to his discharge on December 21, 1972, had been a teacher at the Wilson High School in the Tacoma School District No. 10 for over 12 years, and had received favorable evaluations of his teaching throughout this time. (Findings of fact Nos. 1 and 2.) The court further found that "while plaintiff's status as a homosexual [was] unknown to others in the school," his teaching efficiency was not affected nor did his status injure the school. When, however, it became publicly known that Gaylord was a homosexual "the knowledge thereof would and did impair his efficiency as a teacher with resulting injury to the school had he not been discharged." (Finding of fact No. 9.)
The court further found:
A teacher's efficiency is determined by his relationship with students, their parents, fellow teachers and school administrators. In all of these areas the continued employment of appellant after he became known as a homosexual would result, had he not been discharged, in confusion, suspicion, fear, expressed parental concern and pressure upon the administration from students, parents and fellow teachers, all of which would impair appellant's efficiéncy as a teacher and injure the school.
(Finding of fact No. 10.)
Gaylord assigns error to findings of fact numbers 9 and 10, contending there is no substantial evidence to support either. We do not agree.
First, he argues his homosexuality became known at the school only after the school made it known and that he should not be responsible therefor so as to justify his discharge as a homosexual. The difficulty with this argument is twofold. First, by seeking out homosexual company he took the risk his homosexuality would be discovered. It was *298he who granted an interview to the boy who talked to him about his homosexual problems. The boy had been referred to Gaylord for that purpose by the homosexual friend to whom Gaylord had responded favorably in answering his advertisement in the paper of the Dorian Society. As a result of that interview the boy came away with the impression plaintiff was a homosexual and later told the assistant high school principal about the matter. The latter in turn conferred with plaintiff for the purpose of verifying the charge that had been made. It was the vice-principal's duty to report the information to his superiors because it involved the performance capabilities of Gaylord. The school cannot be charged with making plaintiff's condition known so as to defeat the school board’s duty to protect the school and the students against the impairment of the learning process in all aspects involved.
Second, there is evidence that at least one student expressly objected to Gaylord teaching at the high school because of his homosexuality. Three fellow teachers testified against Gaylord remaining on the teaching staff, testifying it was objectionable to them both as teachers and parents. The vice-principal and the principal, as well as the retired superintendent of instruction, testified his presence on the faculty would create problems. There is conflicting evidence on the issue of impairment but the court had the power to accept the testimony it did on which to base complained of findings. See Jacobs v. Brock, 73 Wn.2d 234, 437 P.2d 920 (1968); Kuster v. Gould Nat'l Batteries, Inc., 71 Wn.2d 474, 429 P.2d 220 (1967). The testimony of the school teachers and administrative personnel constituted substantial evidence sufficient to support the findings as to the impairment of the teacher's efficiency.
It is important to remember that Gaylord's homosexual conduct must be considered in the context of his position of teaching high school students. Such students could treat the retention of the high school teacher by the school board as indicating adult approval of his homosexuality. It would be unreasonable to assume as a matter of law a teacher's *299ability to perform as a teacher required to teach principles of morality (RCW 28A.67.110) is not impaired and creates no danger of encouraging expression of approval and of imitation. Likewise to say that school directors must wait for prior specific overt expression of homosexual conduct before they act to prevent harm from one who chooses to remain "erotically attracted to a notable degree towards persons of his own sex and is psychologically, if not actually disposed to engage in sexual activity prompted by this attraction" is to ask the school directors to take an unacceptable risk in discharging their fiduciary responsibility of managing the affairs of the school district.
We do not deal here with homosexuality which does not impair or cannot reasonably be said to impair his ability to perform the duties of an occupation in which the homosexual engages and which does not impair the effectiveness of the institution which employs him. However, even the federal civil service regulations on which Gaylord relies to show a change in attitude towards homosexuals provides:
[W]hile a person may not be found unsuitable based on unsubstantiated conclusions concerning possible embarrassment to the Federal service, a person may be dismissed or found unsuitable for Federal employment where the evidence establishes that such person's sexual conduct affects job fitness."
2 CCH Employment Practices Guide ¶ 5339 (1975). It must be shown that the conduct of the individual may reasonably be expected to interfere with the ability of the person's fitness in the job or against the ability to discharge its responsibility. 2 CCH Employment Practices Guide, supra. These principles are similar to those applicable here. The challenged findings and conclusions are supported by substantial evidence.
Affirmed.
Wright, C.J., Hamilton, Stafford, and Brachtenbach, JJ., and Kale, J. Pro Tern., concur.