Crackdown disciplines 230 Ely Community College pupils
More than 230 out of 1,250 pupils were removed from classes at a school in Cambridgeshire as part of a head teacher's zero-tolerance programme.
About one in five City of Ely Community College pupils were disciplined on the first day of a crackdown on "low-level disruptive behaviour".
The new policies were introduced by head teacher Catherine Jenkinson-Dix.
Pupils not wearing the uniform or using mobile phones were taken out of class and made to work in a school hall.
Governor Ben Gibbs said parents had been warned of the new policy, brought in on Monday, which also punished chewing or eating in class.
Mr Gibbs said the number of offenders fell to fewer than 200 on Tuesday and by Thursday it was down to 115.
He said senior staff had studied other schools' use of similar zero-tolerance policies and decided to follow suit.
Teachers, most parents and the majority of pupils approved of the new approach, he added.