South Yorkshire Chief Constable Meredydd Hughes said senior officers had met school heads to discuss why so many "people of school age" were involved in the protests against a rise in university tuition fees.
Thousands of students from the region protested against the coalition Government's proposals, taking part in demonstrations at campuses in Sheffield, Leeds, York and Hull.
Many also travelled to London, where organised marches descended into violent clashes between activists and police and resulted in one mob attacking a car carrying the Prince of Wales and the Duchess of Cornwall.
Mr Hughes said the protests in South Yorkshire were "well organised and well behaved, with only a few incidents", but he also estimated that policing them had cost his force in the region of 500,000.
He added that there was a "hidden cost" of having to withdraw officers from their normal duties to ensure the protests remained peaceful.
The Chief Constable's comments are recorded in the minutes of a South Yorkshire Police Authority meeting, where members considered the force's performance during 2010.
Last month Mr Hughes told the Yorkshire Post that he feared the force faced a "long, hot summer of discontent" as opposition grows to the Government's spending cuts.
Security is expected to be tight when the Liberal Democrats hold their spring conference in Sheffield in March, and the police authority has considered applying for extra funds from Whitehall to help pay the bill.