POLICE said that two of the three pupils arrested after protests at Pontllanfraith Comprehensive School were reprimanded and released.
The boy and a 15 year-old girl were arrested on suspicion of obstructing a highway.
Another 15 year old girl was arrested on suspicion of obstructing a highway and for public order offences.
She remains in custody.
Hundreds of pupils abandoned classes this morning to take part in the protests against reported redundancies.
Pupils gathered this morning in the school yard, but later a group moved outside the school gates.
Teachers tried to usher the pupils back into the school, but at around 11.30pm, police were called in to help.
Ten officers arrived in two police cars and and squad van and ushered the children back into the school.
Pontllanfraith was put into "special measures" in January 2007 but two weeks ago that ended after inspectors said the school had made good progress.
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