The damning report on Cardiff's Llanederyn high school came just weeks after it was saved from closure under council reorganisation plans.
Staff and pupils at the 886-pupil school only heard of their reprieve the week of their inspection. However, there was not much to celebrate in the report published this week. In four out of seven key questions, including achievement, effectiveness of teaching and leadership, the school scored a low grade 4.
Leaders at the school, where 27 per cent of pupils are eligible for free school meals, were said not to have fully addressed issues raised in a 2000 inspection. But Tim Cox, NASUWT national executive member, this week claimed the timing of the inspection in April had been unfair.
He said: "We will start work immediately with the school's management and Cardiff education authority on these issues."
In the report, inspector Julia Longville said on-going behavioural problems of a "significant minority of pupils" was affecting the learning of others, with negative attitudes by pupils who lacked interest and motivation. She said boys were the worst behaved.
Pupil attendance at the school is just over 85 per cent annually - well below the national target of 92 per cent. Inspectors found there had been an improvement in the number of KS3 pupils achieving at least grade 5 in English, maths and science.
There had also been an upward trend in the pupils gaining at least grade C in maths, science and English at GCSE.
But overall GCSE results are falling, with the number of pupils gaining at least five grades at A*-G dropping from 81 per cent in 1999 to 78 per cent in 2005.
Staffing problems in 2005 meant results in English at both KS3 and KS4 were not as good as science and maths. Inspectors also found a lack of consistency in how teachers applied positive behaviour management plans.
The school must make changes to its improvement plan within 45 days.
A spokesperson for the school said: "We all thought the school was going to be closed - it is recognised that improvements are needed in achievement, behaviour, attendance and some aspects of leadership."
It is rare forJEstyn to recommendJspecial measures for schools. There have only been around a dozen in Wales since 1996, compared with 2,000 given by Ofsted in England.