"A local authority much have regard to the desirability of such a formula being simple, objective, measurable, predictable in effect and clearly expressed" (The School Funding (Wales) Regulations 2010, Section 10 paragraph 2)
Did the authority provide a written explanation of the Cardiff funding formula? Yes.
Is the formula measurable? Is it predictable? Yes.
"The regulations require that 70 per cent of the funding must be distributed on the basis of pupil numbers. (School Funding in Wales Research Briefing August 2018)
Is 70% of school funding based on pupil numbers? The formula states that the majority is based on pupil numbers and it is clear by looking at the numbers that this is true. Cardiff uses a combination of pupil numbers and pupil:teacher ratios. Many elements' funding is based on pupil numbers such as support staff calculations, supply staff, grounds maintenance, and some elements of facilities maintenance. While it is not explicit that 70% is based on pupil numbers, it certainly seems implicit in the way the formula is structured.
It is also clear from the formula that there is a base level of funding for children in particular year groups across all schools so Cardiff is ensuring "the same funding for pupils of the same age irrespective of the nature of the school which they attend" (The School Funding (Wales) Regulations 2010, Section 23 paragraph 1b).