20.—(1) For the purpose of determining (including redetermining)—
(a)budget shares for nursery schools maintained by it;
(b)amounts to be allocated in respect of nursery classes in schools maintained by it;
(c)amounts to be allocated to relevant early years providers in its area; and
(d)amounts to be allocated in respect of community early years provision in schools maintained by it,
a local authority may use factors or criteria which differentiate between different categories or descriptions of school or provider on the basis of unavoidable costs.
(2) In particular, a local authority may include an additional sum in the budget share of each nursery school maintained by it.