dissent and vote to affirm in the following memorandum by Casey, J. Casey, J. (dissenting). The determination of the commissioner denying tenure to the petitioner is not arbitrary, and Special Term was correct in affirming it. The petitioner was employed as a full-time probationary elementary teacher by the Wallkill Central School District for the 1973-1974 and the 1974-1975 academic years. In September, 1975, she requested and received a transfer to a half-time or part-time learning disabilities position. Petitioner claims the change was undertaken upon assurances from her building principal and the superintendent of schools that her probationary service time would continue on a one-half basis (one-*980half day teaching for the school year to equal one-half year towards tenure). The building principal denies any such promise; the superintendent of schools confirmed his promise in writing a month or so after the petitioner had undertaken her part-time duties, in which capacity she continued for one and one-half years. In January, 1977, she returned to her full-time position as an elementary teacher and served therein until June, 1977, when she was notified of her termination effective July 30, 1977. Thus, the petitioner compiled a total of two and one-half years of full-time, probationary status as an elementary school teacher and needs credit for her part-time assignment if she is to obtain tenure by acquiescence or estoppel under section 3012 of the Education Law. No collective bargaining agreement is involved herein (see Matter of Schlosser v Board of Educ., 62 AD2d 207, affd 47 NY2d 811). The petitioner’s claim, therefore, depends entirely on the statutes and case law. Furthermore, this is not a situation where the petitioner served her full three-year probationary period with the school board’s acquiescence and then converted or was assigned to part-time teaching duties, which would still preserve the tenure she acquired from three years’ probationary service. This distinguishing fact renders the holdings in Matter of Matthews v Nyquist (67 AD2d 790) and Matter of Dwyer v Board of Educ. (61 AD2d 859) inapposite. The basis for the commissioner’s ruling herein is that teaching service in a part-time position, even with the consent or in reliance on misinformation supplied by school officers, can never be counted toward tenure. Tenure can only be acquired by actual service beyond the term of probation (Matter of Mugavin v Nyquist, 48 AD2d 727, 728). The decision of the commissioner herein is not only not arbitrary, it is in conformity with law. (See Matter of Rosenberg v Board of Educ., 51 AD2d 551, holding that necessary service for tenure must be' actual full-time employment.) The judgment should be affirmed.