The arrests capped a day in which hundreds of students and others marched on the statehouse and rallied outside the Capitol before many of the activists moved the demonstration inside the building, clogging hallways in and around the rotunda.
One group chanted, "No cuts, no fees. Education must be free," as they sat crossed-legged on the black-and-white tiled floor of the statehouse.
The California Highway Patrol, which provides security for the building, said the demonstrators had a permit to protest inside the Capitol until 5:30 p.m. local time, and then were ordered to leave.
Police warned the protesters seven times after the building closed at 6 p.m. that they faced arrest for trespassing if they failed to disperse, and officers moved in to begin taking the demonstrators into custody at about 7:30 p.m.
"We wanted to give them every opportunity," CHP Captain Andy Menard said, adding that the estimated 45 to 50 demonstrators arrested were all given one last chance to leave the building before they were taken into custody.
"The ones who didn't are going to jail," he said.
The demonstration drew words of support from Governor Jerry Brown, a Democrat, who issued a statement saying the protesters "are reflecting the frustration of millions of Californians who have seen their public schools and universities eroded year after year."
He urged public support for a ballot initiative in November calling for a temporary tax increase to raise additional revenues for public education in the state, which is facing a $9.2 billion budget shortfall.
Some of the demonstrators also sought to collect signatures for a petition to put a measure on the ballot that would impose an extra 1 percent tax on individuals with annual incomes of $1 million or more.
(Additional reporting by Adam Weintraub; Editing by Steve Gorman and Tim Gaynor)
