this doesn’t work like you think it would. many school districts that used this funding model got absolutely fucking destroyed when covid happened and families either moved or parents moved their kids to private schools.
it creates downward pressure: as kids leave schools for reasons, funding drops, so the schools make cuts and the quality of education drops. then more parents take their kids out of school, funding drops more, rinse and repeat.
if you expect your funding model to span multiple decades then yes, you absolutely need to factor in “edge cases” like covid. climate change will have an effect on school attendance, guaranteed.
any system that seeks to create an “efficient funding” model will always fail our children. schools are not businesses and cannot function as one.