OPINION OF THE COURT
Memorandum.
The order of the Appellate Division should be reversed, with costs, the judgment of Special Term dismissing the petition reinstated and the question certified answered in the affirmative.
Section 3012 of the Education Law provides that “Teach*875ers and all other members of the teaching staff * * * shall be appointed * * * for a probationary period of three years” (subd 1, par [a]), after which they may be recommended for appointment on tenure (subd 2). The commissioner has long adhered to the principle that only full-time teaching service fulfills the statutory requirement of a three-year probationary term so as to entitle a teacher to a tenured appointment. Inasmuch as the statute does not expressly provide a probationary term for part-time teachers, the denial of tenure credit for part-time service is not arbitrary. While public policy does not prohibit a contractual provision giving tenure credit for part-time service (Matter of Schlosser v Board of Educ., 47 NY2d 811), nothing mandates credit in the absence of such provision. Having failed to complete the probationary term with the required service, petitioner may not claim tenure by estoppel or acquiescence.
Chief Judge Cooke and Judges Jasen, Gabrielli, Jones, Wachtler, Fuchsberg and Meyer concur.
Order reversed, with costs, the judgment of Supreme Court, Albany County, reinstated and the question certified answered in the affirmative in a memorandum.