N.J. Stat. Ann. § 52:18A-112

6. A member of a State administered retirement system or an employee of a board of education, as defined in N.J.S.18A:1-1, regularly scheduled to work 20 or more hours per week may become a participant by filing an application for enrollment in either the Variable Division or the Fixed Division, or both, in accordance with rules and regulations established by the council. An employee regularly works less than 20 hours per week if, for the 12-month period beginning on the date the employee's employment commenced, the employee's employer reasonably expects the employee to work fewer than 1,000 hours of service, as defined under section 410(a)(3)(C) of the Internal Revenue Code of 1986 (26 U.S.C. s.410(a)(3)(C)), and, for each plan year ending after the close of that 12-month period, the employee has worked fewer than 1,000 hours of service.