N.H. Rev. Stat. Ann. § 261:92

The director shall have the authority to prescribe special rules relative to registration of vehicles owned and driven by the government of the United States, the state, or by any county, city, town, regional planning commission, school district, volunteer fire department, eligible nonprofit corporation operating transportation under contract with the department of transportation for the public or for elderly or disabled persons, or public or private educational institution used for the purpose of student driver training, and may issue permanent number plates for such vehicles. Said vehicles displaying said number plates shall be deemed to be properly registered under the provisions of this title and may be driven upon the ways of the state without further registration or subsequent number plates.