Official figures released by the then Department for Education and Employment in January showed 4,000 vacancies existed in schools in England and Wales. But new reports suggest this figure has risen to 4,600, despite ministerial assurances the posts will be filled by next month.
NAHT general secretary David Hart said: 'I think it's highly unlikely the posts will be filled. Heads have been fighting to recruit staff but we're into the last three weeks before the new term.
'Some will be filled at the last minute and local authorities will be fighting hard since the only alternatives are supply cover or sending pupils home.'
'Lambeth reports it will fill nearly all vacant posts and Portsmouth is on track to meet at least three quarters.' he said.
'Summer is always a very busy time for teacher recruitment but all the evidence we have suggests schools are filling their vacancies ready for the new term.'