N.J. Stat. Ann. § 18A:18B-5

The board of trustees of any school board insurance group shall have no fewer than three nor more than 15 trustees. Each trustee shall be a natural person 18 years of age or older who is a resident of this State. A majority of the trustees of any group shall be members or employees of member boards of education, provided that any trustee who ceases to be a member or employee of a board of education may be allowed to serve for not more than 90 days following cessation without violating this provision.