A problem with performance related pay for teachers, as for any other category of workers, is that for it to be accepted it needs to be fully funded. But this is not consistent with the Government's desire to control expenditure on public services and since salaries in schools are the largest item of expenditure, a rise in the salary bill has a number of consequences for other school budgets. This week the contradiction became too severe for the Secretary of State for Education and Charles Clarke called for teachers salaries to be capped.