Moisés Paredes speaks for a movement which has defied police brutality to put education reform high on the election agenda

On Wednesday, Moisés Paredes helped organise a march of 100,000 protesters through the streets of Chile's capital, Santiago, calling for free university education. That night, he organised a press conference to defend the occupation of dozens of polling stations before Sunday's presidential primaries. On Thursday, he and his fellow activists were roused by riot police in a dawn raid.

Next week, he'll be back at school.

Paredes is the 18-year-old national spokesman for a collective of secondary school children, and a prominent member of a new generation of political activists who have led a string of massive protests – and helped make education reform a key issue in the presidential primaries.

"I've not slept in 36 hours, and yes, I'm hungry," he says, devouring a hamburger and chips while fielding a string of phone calls from fellow student leaders, journalists – and his mum.

100,000 students and public-sector workers protest for education reform in Santiago, Chile. Photograph: Pablo Rojas Madariaga/NurPhoto

The students argue that education is a basic right, while the government led by the president, Sebastián Piñera, has defined education as "a consumer good" – and the gulf between those two positions has shifted little during the course of the now two-year-old protest movement.

Police tactics against the students – both on the marches and while removing the students from occupied schools – have been marked by severe brutality, including shooting the students in the face with paintballs and indiscriminately beating them with truncheons. Paredes said that during the removal of students from the prestigious Carmela Carvajal school police dragged girls out by their hair.

"It is typical of this government, and especially Andrés Chadwick [the minister of the interior], who think they can end this conflict with violence and instead are just adding more fuel to the fire," said Paredes. "They are making the student movement more radical, leading to students seizing more schools and more universities."

When the police arrived on Thursday, Paredes hurriedly stuffed a change of clothes and a toothbrush into a white plastic shopping bag, which he now carries as he moves from one meeting to another. Along the way he fired off a string of potshots at Piñera on Twitter.

Chilean police detain a woman during the eviction of protesters from a school in Santiago. Photograph: Ariel Marinkovic/EPA

Paredes described the president – who is ranked by Forbes as the world's 589th richest person with a net worth of $2.5bn (£1.6bn) – as an "intransigent businessman" who has sold Chile to the economic interests of a tiny elite.

"It is abysmal that someone like him can have so much money and others do not have a roof or even basic needs like public education," said Paredes.

"The state has forgotten their duties and let the market intervene across the board, putting profits before everything. You see this in healthcare, natural resources, education."

Asked about his own net worth, he whips out his wallet to show that it contains nothing but a student bus pass.

Paredes knows well the cost of being a student activist. In 2011, he was evicted from his school by then mayor Cristián Labbé, a former Pinochet bodyguard and retired army colonel who enacted a harsh crackdown on student activism.

For a year Paredes was banned from the classroom while his lawyers argued his case all the way to the Chilean supreme court, which eventually ruled in his favour.

He admits that his mother still worries for his safety. "She tells me to be careful. At first she didn't want me to be involved in the protests – she thought it would be too dangerous. You know she is from the other generation of the [Pinochet] dictatorship and they still have the fear that people who become politically involved will then be found [dead] under a bridge or disappeared," said Paredes.

Police fire water cannon at student protesters in Santiago, Chile. Photograph: Zuma/Rex Features

"I was never involved in politics until two years ago. No one from my family is politically active. These protests have been my training.".

While the students' primary demand – free university education for all – has yet to be achieved, education reform has been catapulted to the top of the Chilean political agenda.

Several university directors have been jailed for running illegal, for-profit institutions, and Universidad del Mar, a private university that had more than 15,000 students, was stripped of government accreditation and essentially shut down by government regulators.

The leading presidential candidate Michelle Bachelet recently outlined a multi-year transition plan that would phase in higher taxes to pay for universal, free university education.

Camila Vallejo, one of the most prominent leaders of the initial 2011 protests, is now campaigning for a seat in the Chilean congress. Vallejo, a member of the Communist party, is one of several former student leaders now running for office.

For Paredes, the education protests have completely changed his outlook on life. Before the student uprising, he spent his free time taking singing classes, honing his tenor voice in school choruses and at public concerts. "Now, with all the protests, I have to dedicate my time to interviews," said Paredes. "Now my voice is used to communicate other things."