SANTIAGO - About 50 people were arrested here Thursday in a clash between police and students demanding a reform of the education system.

Chilean police used tear gas and water cannons to deter the protesters, more than 5,000 high school students and some university students.

Police said at least three officers were injured, including one in serious condition.

"We called for this protest to demand the right to learn and to access education," said Emiliano Salas, spokesperson for the Coordinating Assembly of High School Students, which organized the demonstration.

Thursday's protest, the first called by student groups this year, followed the more than 40 massive street marches last year by middle school and university students protesting low budget funding for education.

Some of the protests drew more than 100,000 people, paralyzing major cities and resulting in clashes with police.

"This year, we are beginning earlier the call for protests to demand a better education. Students, workers and all the citizens will protest together," Salas said.

Chilean President Sebastian Pinera called on students to stop the protests in late January as he issued a law granting 110,000 students tuition loans.

"I want to ask you to make 2012 a more constructive year. If protests, violence and 'seizures' continue, we aren't going to move forward," Pinera said. But students rejected the plan as not addressing the main problem.

Now that the summer vacation is over in Chile, more protests are expected to come. Both high school and university student groups have said they are preparing a demonstration in April.