Britain's largest public sector union Unison has joined the row over Education Bradford's bonuses and demanded its contract is not renewed.

The results for the last academic year reveal the company, responsible for the performance of Bradford schools, failed to match or better more than 30 targets, but still received more than £250,000.

Targets missed included the proportion of seven-year-olds who reached the expected level in reading and writing, the numbers of children who attained benchmark figures in maths, English and science at the ages of 11 and 14, and the number of pupils who achieved five A* to C GCSEs, including English and maths.

In 2001, when the company, owned by Serco, took on the £360 million, ten-year contract, it stated its key aim was to see the district's schools match or better national benchmarks in crucial areas. Steve Torrance, Unison's regional officer for Bradford, said: "The people of Bradford need to be clear that this is not just one year of Serco failing to meet the agreed targets but the latest in a long list of failures.

"It is also a timely reminder that private companies motives are not necessarily in the best interests of driving up the education standards of children."

Mr Torrance said he had been "incredulous" on learning Education Bradford could earn a further £385,000 if targets yet to be decided were met, and called on Bradford Council to bring education back under its control when Education Bradford's contract ends in 2011.

Education Bradford did hit ten targets this year, including reducing the percentage of schools in Ofsted categories of concern and the number of 16 to 18-year-olds not in education, training or employment.

An Education Bradford spokesman said: "Performance improved on 33 out of 44 targets in 2007 compared with 2006. This means schools are performing better overall year on year. When compared with performance since 2001, there has been significant improvement."

Sue Colman, Bradford Council's director of learning services, said: "The incentive payment Education Bradford has received is in line with the contract. It represents the level of reward for targets met that has been agreed since 2005."