Education inspectors - who themselves witnessed one teacher being attacked - warned the Secretary of State for Education, Gillian Shephard, that the school was lurching "out of control".
When local education officers were informed, they investigated themselves yesterday, saw another assault - and ordered Ridings to shut its doors.
The Halifax school is the second to be closed because of indiscipline within three days, following similar action at Manton primary school in Nottinghamshire - brought about by indiscipline and teachers' refusal to teach disruptive pupils. The closures are unprecedented in recent educational history.
Senior inspectors yesterday briefed Mrs Shephard on the main findings of their report, which concludes that the school was heading "out of control" and that pupils could be in physical danger. The Ofsted document, which will be published next Wednesday, will point out that there was no register to assess the number of children attending the school each day. It is not clear whether they will declare Ridings a "failing" school, take it out of the control of the local authority and send in a "hit squad" of government- appointed teachers.
The woman alleged to have been attacked by a 15-year-old boy yesterday was believed to be a French national in her twenties working as a supply teacher. Another assault is said to have involved a pupil slamming a door in a teacher's face.
Yesterday the designated new headteacher, Peter Clark, said his priority would be to install a semblance of normality in which "effective learning" could take place. He is due to start if and when the school re-opens on Wednesday. The school's 33 teachers, members of the National Association of School Masters Union of Women Teachers, meanwhile voted overwhelmingly to strike unless 12 pupils were expelled.
Nigel de Gruchy, the union's general secretary, said he was "staggered but not surprised" by the news that education officials were warned on Wednesday about the deteriorating situation at the Ridings, but took no action until yesterday. "This bears out everything I have been saying that the teachers have been asking for support from managers but not getting any."
Members wanted 12 pupils excluded in order to preserve acceptable standards of health and safety . Nothing less would prevent them walking out on strike he said.
The result of the NASUWT ballot - 33 voting forms were distributed and 31 returned all with yes votes - gives the union authority to call a strike any time within 28 days, provided they give a week's notice of their intention to walk out.
But some parents have blamed the disturbances on the teachers.
Linda McDermott, whose sons Dennis,13, and Steven,15, are at present excluded from the Ridings, said the closure was "ridiculous". She said: "I think the teachers are being pathetic - they just don't seem to be able to cope. I was expecting something like this. The only way to go forward from here is to start again with new teachers."
Letters, page 21Reuse content