N.H. Rev. Stat. Ann. § 621:26

A minor erroneously committed to the center may be discharged by a justice of the superior court, upon petition of the county attorney or a selectman of the town or mayor of the city in which the minor resides, when continued commitment is unnecessary. Upon petition to the superior court by the division or the board, the court may review the case of a child, modify or amend the order of commitment, or order the release of the child.