Students are planning another wave of protests today, with more than 20,000 school, college and university students planning to walk out of classes at 11am. A series of occupations, rallies and marches have also been planned.

Protests are against the rise in university tuition fees.

Tension over today’s protests is mounting after the last  rally descended into violence when a group of activists smashed windows, threw missiles and lit fires at 30 Millbank – the Conservative Party headquarters.

The violent protest led to more than 60 arrests and dozens were injured and taken to hospital. A student will appear in court today accused of throwing a fire extinguisher from a seventh floor rooftop.

Police have are trying to keep tabs on today’s protest and deputy Prime Minister Nick Clegg has urged students to call off the demonstrations.

However marches have been organised in cities including London, Birmingham, Glasgow, Manchester and Cambridge.

Students will gather in London’s Trafalgar Square before marching to Parliament to protest outside the Liberal Democrat headquarters and later in Downing Street.

Musician Jarvis Cocker will join a Royal College of Art students’ union protest in Kensington, west London.

The Lib Dems are particular targets as they won much of the student vote by vowing not to raise tuition fees. The government now plans to charge students as much as £9,000 per year from 2012.

Students in Sheffield will present Lib Deb leader Kick Clegg with a letter reading: “No amount of twisted reasoning from either you or Vince Cable can hide what everyone can see: you have lied to us. We call on you to withdraw LibDem support for Conservative cuts to our education system, or face the disappointment and anger of a generation that has been betrayed.”

Former Met Police commissioner Brian Paddick told Sky News police would “throw the kitchen sink” at the demo to ensure there is no violence.

“There will be many officers there this time round,” he said.

NUS president Aaron Porter told Sky News he wants to keep today’s protests peaceful: “There are no conditions in which violence is acceptable,” he said.

“We saw a couple of weeks ago the anger that students had with regard to the Government’s proposals and tomorrow is another opportunity for students to show what they think about those proposals.

“From my perspective I think it’s really important that the campaign continues its momentum and we continue to hold the Government to account.”

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Related: Student arrested for throwing fire extinguisher during protest