Peter Clark, appointed acting head last week, made his first move to restore order at the Ridings as its governors met to discuss an inspection report that is expected to brand the school a failure.
Calderdale council said that a number of the excluded pupils had been involved in incidents which led to the school's closure.
Mr Clark's action, announced at a council press conference, goes a long way towards meeting the demands of teachers at the school who said originally that they would strike unless 60 pupils were expelled but then reduced the number to around 20.
The inspection report, to be published today by Gillian Shephard, the Secretary of State for Education, is understood to say that the school not only fails to control its pupils but also offers them poor teaching.
The school reopens today for fifth- and sixth-formers and later this week for other pupils under Mr Clark, head of a nearby grant-maintained school. It was closed by Calderdale last Thursday after inspectors said it was in danger of spiralling out of control.
Members of the National Association of Schoolmasters Union of Women Teachers who have voted to strike will be at work today. They have not yet taken a final decision about strike action.
Nigel de Gruchy, its general secretary, said of the exclusions: "We are very pleased. This is a step in the right direction." Earlier, after a meeting with council officials he said that he was optimistic that the council was now meeting the union's concerns.
After meeting his members he said they viewed Mr Clark as "a positive, down to earth man with the right attitudes".
He added that some teachers accepted that they would be criticised in the report of the emergency inspection team which visited the school last week.
Mr de Gruchy said: "Everyone has been blamed and we must take our share of the responsibility but few have blamed the biggest factor of all, the outrageous behaviour of a hard core of unruly children and their families."
Michael Higgins, Calder- dale's education chairman, said the authority could give no "blanket assurances" about expulsions. Each case would be treated on its merit. The school needed "to get its act together" and present a clear case to the independent appeals panel.
Failing schools are normally allowed 40 days to produce an action plan on how they intend to improve. However, Mrs Shephard is likely to use her power to shorten this time limit in the case of the Ridings.
If she is not satisfied with the plan, she can send in a team of education experts to take over from the head who decide whether it should close.
A governors' meeting last night at Manton Junior School in Worksop, Nottinghamshire, failed to resolve the dispute there over a disruptive 10-year-old which has closed the school.
The governors appealed to Nottinghamshire county council to intervene. Members of the NASUWT are refusing to teach the boy.
Prospects for settling the dispute look bleak. Fred Riddell, the education chairman, has written to Mrs Shephard saying he has no legal power to intervene. He said it would be wrong to take money away from other children to pay for one-to-one tuition for the 10-year-old in order to end the strike.