Dozens of rights groups in the United Kingdom are calling for an end to censorship of campaigning for Palestine at schools, saying countless students have faced reprisals for speaking up for the cause.

In an open letter reported by the leftist Morning Star daily, 26 organizations have expressed concerns about efforts to silence solidarity with Palestine following a crackdown on pro-Palestinian protests in schools last month.

Penned by Palestine in Schools and published at the weekend, the letter says the group has received countless cases of students being reprimanded, suspended and even expelled for publicly supporting the cause or displaying the Palestinian flag.

In some schools, discussions on Palestine have been outright banned, the letter reports, while students have faced threats of being reported to the government’s anti-extremism program Prevent.

“Instead of praising their students for taking an interest in the world around them, schools are actively preventing their students from developing themselves politically,” the letter, signed by Black Lives Matter, policing monitoring group Netpol and anti-Islamophobia group Mend, says.

“We demand that the government abandon its censorious and repressive approach to controlling such campaigning in schools,” the letter concludes.