Egyptian authorities have released without charge a group of school pupils who had been arrested a day earlier for protesting at their school, security sources told Ahram Online.

Seven pro-Muslim Brotherhood pupils were arrested on Monday as they arranged a protest at a preparatory school east of Cairo and refused to attend their classes. 

Egyptian children attend prepatory school between the ages of 12 and 14.

Political disorder has spilled over into schools and universities in Cairo and elsewhere since the start of the new academic year last week.

Thousands of students sympathising with toppled Islamist president Mohamed Morsi staged protests in several cities, and many have been arrested, security forces said.

Dozens were wounded on Sunday as groups of students for and against president Morsi clashed on at least three campuses: at Cairo’s Ain Shams University, at Zagazig University in the town of Sharqiya, and at a university in the city of Tanta.

Egypt has been rocked by bitter upheaval since the army ousted Morsi on 3 July following mass protests against his year-long rule, unleashing violent street showdowns that have killed hundreds, mostly Islamists.

A sustained crackdown by security forces has severely crippled the Brotherhood's ability to muster street support, prompting them to turn sights on campuses, traditional hotbeds of political activism.

Over 2,000 people, mostly supporters of Morsi's Muslim Brotherhood, have been arrested over the past two months.