ALMOST 200,000 children are at “underperforming” primary schools following controversial changes to SATs tests, official figures showed yesterday.

In total, 665 mainstream primaries in England fell below the government’s lowest acceptable standard this year, according to the Department for Education (DfE).

But teaching unions warned that the figures were unreliable because of the changes, which they labelled “chaotic” and “badly implemented.”

Schools are considered to be underperforming if fewer than 65 per cent of pupils fail to reach the expected standard in reading, writing and maths, or if they fail to make sufficient progress in these three key areas.

The findings follow a turbulent year for primary assessment, including the introduction of major changes to “toughen up” the tests and concerns raised by teachers and school leaders about pressure on pupils.

Association of Teachers and Lecturers assistant general secretary Nansi Ellis said: “Schools must not be judged on this year’s SATs results, which were totally unreliable and were the culmination of a chaotic mess of badly implemented and badly designed tests.”

National Association of Head Teachers leader Russell Hobby said the data was “not worth the paper it is written on.”

He added: “Delayed and obscure guidance, papers leaked online, mistakes in test papers and inconsistent moderation made this year unmanageable for school leaders, teachers, parents and pupils.”