N.J. Stat. Ann. § 18A:18A-9

Periodic solicitation of bids. Every board of education shall, on an annual basis or at such lesser intervals to be fixed by it, solicit by public advertisement the submission of bids for the provision or performance of goods or services which are and which under N.J.S.18A:18A-4 can be contracted to be provided or performed only after public advertisement for bids and bidding therefor and all contracts for the provision or performance of such goods or services shall be awarded only in that manner.