StatsWales
For data on population, school budgets, school numbers, and budget outturns (deficit and surpluses).
Freedom of Information Request Summer 2019
For funding information from 2016-2020, provisional figures for the budget outturn 2018-19, and projected pupil numbers and surplus capacity.
My Local School
For Free School Meal rates for each school, and for language.
National school categorisation system: support categories
For support categories for each school.