Where the local education authority resolve that any of the children attending an elementary school within their area are unable by reason of lack of food to take full advantage of the education provided for them, and have ascertained that funds other than public funds are not available or are insufficient in amount to defray the cost of food furnished in meals under this Act, they may apply to the Board of Education, and that Board may authorise them to spend out of the rates such sum as will meet the cost of the provision of such food, provided that the total amount expended by a local education authority for the purposes of this section in any local financial year shall not exceed the amount which would be produced by a rate of one halfpenny in the pound over the area of the authority, or, where the authority is a county council (other than the London County Council), over the area of the parish or parishes which in the opinion of the council are served by the school.