Students who took part in an anti-war protest have been suspended from school just weeks before sitting their GCSE exams.
At least five students from Blatchington Mill School in Hove have been given fixed-term expulsions.
The move has angered parents who feel their children have been made scapegoats after a walkout at the school got out of control.
About 200 pupils charged out of classes on Friday, with dozens leaving the school grounds to take their protest to the streets.
Teachers tried to stop pupils leaving the school by closing gates leading to Holmes Avenue but the youngsters ran across playing fields and left by the main entrance in Nevill Avenue instead.
A letter sent to parents on Monday said the youngsters were suspended for disobeying staff, leaving the school without permission and putting the health and safety of other students at risk.
Glen Whittaker's son Adam, 15, is among those suspended until mid May, when GCSE students begin study leave.
Mr Whittaker, of Hove, said: "This is the most crucial year of my son's education and he needs to be in classes. He is very upset by what has happened and thinks there is no way he will pass his exams now.
"All he did was express his views on the war. It was just youthful idealism."
Sarah McMurray, 15, of Arthur Street, Hove, has also been temporarily excluded.
Her mother, Sally, said: "I feel proud Sarah has taken such an interest in current affairs. In protesting she behaved honourably and it's wrong for her to be punished so harshly for that.
"Her education is being put in jeopardy at the most crucial time of her life, simply because she exercised her democratic right."
Sarah said: "We didn't do it to go against the school - we did it because we wanted our voices to be heard. We were rebelling against the Government because we feel it is rebelling against us."
Headteacher Neil Hunter said all the suspended pupils would be allowed back into school to sit their summer exams.
He said: "If we feel a student has behaved inappropriately, we are left with several courses of action. In this case, nobody has been permanently excluded and no pupil has been prevented from taking their exams.
"Nobody has been suspended for their involvement in this incident alone.
"In every case, Friday's protest marked a culmination of events."
Mr Hunter said pupils approached him two days before the protest informing him of their intentions.
He said: "I felt proud the students wanted to make their opinions known and I commended them.
"But I told them I had a duty to look after the well-being of everyone at the school and suggested a petition would be a safer alternative.
"They agreed with me at the time. I have no problems with students stating their views as long as it is done safely."
Parents wishing to appeal against the suspensions can do so before a disciplinary panel of three school governors. The panel will meet in the next two weeks.
Chairman of governors Mark Worgan said: "The panel will consider each case individually and can meet six to 15 days after the suspension date."
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