Section 31A. The trustees of the Essex agricultural and technical institute, the Bristol county agricultural school and the Norfolk county agricultural school may, if in their judgment the circumstances warrant, and it is not otherwise provided for, pay, in whole or in part, the costs of transporting any pupil who resides in a town in the county of Essex, the county of Bristol, or the county of Norfolk, as the case may be, between the town and the school, and such expenditure shall be deemed to be a proper maintenance item.