The teaching unions have bitterly opposed both privatisation and voucher systems, but the offer of local control implicit in charter schools is proving attractive to their members, supporters say.

The American Federation of Teachers, the second-largest US teachers’ union, this month cautiously endorsed charter schools which operate independently within the state system and are intended to cut bureaucracy. However, it did call for studies to show if they actually improve students’ performance.

In California, which has pioneered charter schools and is home to nearly half of the 225 across the country, they appear to be winning converts. When the state earlier this year lifted a 100-school ceiling, the California Teachers Union opposed the move, continuing a policy of keeping the numbers as low as possible.

But teachers’ representatives in Los Angeles chose not to object. “Teachers feel they have ownership of the school. They can be more responsible, as well as being more accountable,” said Yvonne Chen, the principal of Vaughn Next Century Learning Centre, LA’s first charter school. “It is teacher empowerment. ”

Half the US states now have charter laws on their books. Some schools exercise limited financial management and choose to continue union contracts. Others renegotiate deals with teachers. At the 1,150-pupil Vaughn school, based in a poor area of the city, the 49 teachers set their own salaries low enough to create a $1 million surplus on its $5m budget. It is touted as a major success story. However, the Edu-Train Charter School, set up to handle school drop-outs, collapsed last year leaving the Los Angeles district and the state quarrelling over a train of debts.