School funding formulas have been applied across a number of countries for at least the last 50 years. A national funding formula (NFF) was introduced in England in 2018 and aims to provide a platform for fair funding across the country. This study explores the variations in the NFF's high needs block (HNB) funding and examines links with the use of specialist provision by English local authorities (LAs) for children with special educational needs and disability. The findings demonstrate significant and continuing differences in HNB funding between demographically similar LAs, notwithstanding a £3.5 billion (75%) HNB increase in real terms in the decade since 2013, which could have supported a shift towards a more equitable position. Published HNB funding for 2023-24 now varies by up to £49m in comparator LAs. Differences are largely the result of the persistent use of a historical factor in the formula and a ceiling on levels of income growth for lower funded LAs. The research also shows a significant link between HNB funding and the use of specialist provision. The discussion investigates how far the UK government's policy commitment to a more equitable system of HNB funding is matched by the reality, and the degree to which funding is based on need rather than demand or history.