This is an appeal from a judgment of the district court of Travis County that set aside an order entered by the Board of Trustees of the Teacher Retirement System of Texas. The Board’s order denied Bert Cottrell’s application for purchase of credit for out of state teaching service pursuant to Tex.Educ.Code Ann. § 3.26(a) (1972). We will affirm the judgment of the district court.
At the time Cottrell applied to the Board to purchase credit for his out of state teaching, § 3.26(a) provided as follows:
“Any member of the retirement system who has been employed as a teacher or as an auxiliary employee in any public school system maintained in whole or in part by any state or territory of the United States or by the United States for children of United States citizens may purchase equivalent membership service credits under this retirement system for such service.” Tex.Laws 1975, ch. 19, § 3.26(a), at 37.
The facts are not in dispute. From June, 1950, until June, 1953, Cottrell was an instructor of chemistry in the Department of Physics and Chemistry at the United States Military Academy at West Point. The United States Military Academy is a fully accredited institution granting academic degrees at the undergraduate level. During Cottrell’s tenure as instructor at West Point, he was a commissioned officer in the United States Air Force assigned to West Point where he taught cadets on a full-time basis.
Following the termination of his duties as instructor at West Point and his separation from the Air Force, Cottrell became a member of the Teacher Retirement System of Texas. In January, 1977, Cottrell completed ten years of service in Texas as a member of the Retirement System, and became eligible to purchase membership service credits to which he was entitled under the Retirement System. Prior to his application for out of state teaching service credit, Cottrell purchased five years of creditable service for active military duty as authorized by Tex.Educ.Code Ann. § 3.23(c). Those five years of credit covered time other than that spent in teaching at West Point. Cott-rell, pursuant to § 3.26(a), applied to the Board for the right to purchase membership service credits for his three years of out of state teaching at West Point. The administrative agency applied the law to the undisputed facts and determined to deny Cott-rell’s application.
The district court entered judgment reciting “ . . . the order made by the Board of Trustees of the Teacher Retirement System of Texas denying [Cottrell’s] application for purchase of credit for out of state teaching pursuant to Education Code Section 3.26, is in violation of the said statute . . .” The judgment of the district court overturned the order of the Board and ordered the Board to approve Cottrell’s application for purchase of credits for out of state service.
The Retirement System attacks the judgment by one point of error: “The trial court erred in holding that the order of the [Retirement System] denying [Cottrell’s] *930application for purchase of credit for out of state teaching pursuant to § 3.26 of the Texas Education Code was in violation of said statute.”
It should be noticed initially that the Board’s decision, upon undisputed facts, that Cottrell was not entitled to purchase credit pursuant to § 3.26(a) is a conclusion of law. Unlike a determination of disputed fact, an administrative determination of a question of law is not entitled to a presumption of validity. Neither the district court nor this Court is bound by the Board’s construction of § 3.26(a). Social Security Board v. Nierotko, 327 U.S. 358, 66 S.Ct. 637, 90 L.Ed. 718 (1945); Board of Adjustment v. Underwood, 332 S.W.2d 583 (Tex.Civ.App.1960, writ ref’d n. r. e.); Commissioner of Insurance v. Allstate Insurance Company, 579 S.W.2d 553 (Tex.Civ.App. Austin 1979) (writ pending).
Under its point of error the Retirement System argues primarily that Cottrell was not entitled to purchase credit for out of state teaching service pursuant to § 3.26(a) because he was not a teacher and because the Military Academy is not part of any public school system.
Cottrell qualifies under the plain wording of § 3.26(a), as it read at the time of his application, as (1) a teacher (2) employed in a public school system maintained by the United States (3) for children of United States citizens.
From 1950 to 1953 Cottrell taught chemistry in the Department of Physics and Chemistry at the Military Academy. That Cottrell was an officer does not mean that he was not a teacher any more than the fact that he was a teacher means that he was not an officer. When Cottrell taught at West Point, he was both a teacher and an officer. Cottrell’s responsibilities as an instructor in chemistry at West Point were no different from the responsibilities of such a position in any college or university in the country except, as noted by counsel, “ . . . his students were, perhaps, brighter than most and undoubtedly sat up straighter in their seats.” At the time of Cottrell’s application to the Retirement System, nothing in § 3.26(a) excluded from eligibility for purchase of credits a member of the military forces of the United States who taught at a public school and was compensated by the United States Government.
The Military Academy is part of a “public school system.” The United States Government, of course, does not maintain the comprehensive type of school system that each of the states does. The Government, nevertheless, does maintain “systems” of schools. Considering only the Department of Defense, there are, in addition to the Military Academy, the Naval Academy, the Coast Guard Academy, and the Air Force Academy. In addition, the Department of Defense maintains schools overseas for the general education of military dependents. The Military Academy functions as a public college. It is, of course, supported by the United States Government. That the Academy’s primary responsibility is to train persons to become officers in the United States Army does not make it any less a public educational institution. Students at the Academy attend without charge for room, board, tuition, and medical care. Admission is open to all those who meet the qualification!, one of which is United States citizenship.
It is of interest that effective June, 1977, § 3.26(a) was amended to exclude from out of state service credit, “ . . . service [performed by one] while a member of the Armed Forces rendered at any public school, for which service the member was compensated by the United States.” Under the terms of the amended statute, Cottrell would not be eligible to purchase credit for his teaching stint at the Military Academy.
The Supreme Court has recognized the presumption that the legislature in adopting an amendment intends to make some change in the existing law. American Surety Co. of New York v. Axtell Co., 120 *931Tex. 166, 36 S.W.2d 715 (1931). Applying that presumption to this case, the amendment of § 3.26(a) is support for our view that the statute, as it existed prior to amendment, allowed credit for teaching at a public school by one who was in the military service and was compensated by the United States Government.
The Retirement System also argues under its point of error that the provisions of § 3.26(a) are not applicable to teaching time performed by one on active duty for the reason that purchase of credit for active military duty is allowed pursuant to the provisions of § 3.23(c). Section 3.23(c) permitted persons who performed military duty prior to becoming members of the Retirement System to purchase credit for up to five years of time spent in military service. As noticed previously, Cottrell purchased five years of creditable service for his military duty pursuant to § 3.23(c). The five years of credit purchased covered time other than that spent by Cottrell in teaching at the Military Academy.
No language in § 3.26(a), prior to amendment, indicated a legislative intent to bar a person otherwise qualified for credit pursuant to § 3.26(a) because he also could qualify under § 3.23(c). Section 3.23(c) probably reflected the intent of the legislature to recognize in this context the value to society of service in the military. On the other hand, § 3.26(a) was most probably an expression of legislative purpose to encourage experienced teachers to come to Texas and remain here. In Cottrell’s case, both legislative purposes were served. We know of no reason in law to bar him from purchase of credit under § 3.26(a).
The judgment is affirmed.