21.—(1) To the extent that a school’s budget share for a funding period was—
(a)determined by reference to an estimate of the number of registered pupils at the school on a particular date or dates; and
(b)differences between the estimated number of pupils on that date or those dates and the actual number of pupils at the school on that date or those dates were not taken into account in a redetermination of the school’s budget share for that funding period,
the local authority must determine that school’s budget share for the following funding period so as to take into account those differences.
(2) A local authority may determine a school’s budget share for a funding period so as to take into account any other change during the course of the preceding funding period in the data by reference to which the school’s budget share for that preceding funding period was determined, if those changes were not taken into account in a redetermination of the school’s budget share for that preceding funding period.
(3) A local authority may adjust the number of registered pupils used to determine a school’s budget share for a funding period where it is appropriate to do so in order to take into account, wholly or partly–
(a)any reduction or increase in the school’s budget share for the preceding funding period arising from the permanent exclusion of a pupil from the school or the admission to the school of a pupil permanently excluded from another maintained school; or
(b)any increase in the school’s budget share for the preceding funding period arising from increases in pupil numbers during the course of that funding period.
(4) A local authority must include factors or criteria in their formula which satisfy the requirements of this regulation.