But their head, who has been forced to send 150 children home each day because of the staff shortage said he could not see the situation improving until Easter, when five new teachers are due to arrive.
Barrie Whelpdon of the 920-pupil Holywells high school, Ipswich, predicted many other schools would soon follow suit.
He has put years 7, 8 and 9 on an emergency timetable with six fewer lessons per week. Each day, at morning break or lunchtime, some classes go home. Lessons for GCSE pupils have been safeguarded.
Mr Whelpdon claimed that schools were at breaking point. "We are running the system to capacity," he said. "If something does break you cannot repair it quickly."
He took the drastic measure after staff sickness and a shortage of supply teachers meant his deputy was supervising several classes at once in the school library.
He said: "This is a symptom of a wider, national problem. We regret this but we cannot provide adequate supervision or standards of education. So we hve rewritten the timetable."
But one parent, who would not be named, said: "I am angry. Many of our children are coming up to exams and need support. Instead they are being sent home."
Mr Whelpdon said he hoped to go back to a full timetable by Easter, when five new teachers boost this 60-strong staffroom. But three vacancies must still be filled.
Holywells serves a deprived area and has been criticised by inspectors; 27 per cent of pupils claim free school meals and one in five has special needs.
Mr Whelpdon said: "Recruits do not hear enough about the positive side of a school like this. We need teachers who are comfortable working with children who do not have all the advantages. Anyone considering teaching will get great rewards at a school like this."
But until the recruits arrive, pupils will continue to leave early.
Kirsty, 13, said: "In some lessons we repeat things because we have different teachers and they do not know what we were doing before."
Michael, 12, was also anxious about the situation. "Missing English and maths is bad because we need that. The teachers always seem to be changing and we get more homework. I am worried about exams."