That the superintendent of such institute [New Mexico school for the blind and visually impaired], out of the appropriation made for said institute [school], shall pay for the transportation of such children, to and from such institution whenever the parents, guardian or person having control or custody of any such child shall be unable to pay for same: provided, that said board of regents shall prescribe what portion of said appropriation shall be used for said transportation purposes.
NMS § 21-5-6