The trial involves a school run by the Marist community, a Roman Catholic teaching order at the centre of a clerical abuse scandal in Chile. It comes at a time of sustained criticism of the Vatican's response to a decades-long sexual abuse crisis.
Joaquin Benitez, who taught for nearly three decades at a Marist school in Barcelona, wore a black ski mask as he arrived at a Barcelona court for the start of his three-day trial.
Public prosecutors are seeking a 22-year jail sentence for Benitez for allegedly sexually abusing four former students at the school.
Thirteen other former students at the school also accused Benitez of sexual abuse but their cases could not go to trial because the alleged crimes happened too long ago.
Benitez is expected to be questioned on Tuesday.
“We hope that justice will be done even if the court will not be able to repair the damage that was done to the victims,” Manuel Barbero, (pictured below) the father of one of the victims, told reporters ahead of the trial.
The first public accusations against Benitez in 2016 triggered a cascade of other complaints of sexual abuse at two other Marist schools in Barcelona.
In total, 43 complaints were filed against 12 teachers and staff but in the end only Benitez and a school lunch monitor will face trial because the rest of the cases exceeded the statute of limitations.
The Marist community was at the centre of a major clerical abuse scandal, which erupted in Chile in 2017 and led to the resignation of 34 bishops in the Latin American country.
Spain, historically a fervently Catholic country, has been less affected by clerical abuse scandals but a rising number of accusations against priests in schools and seminaries in recent years is starting to erode the wall of silence.
Activists say many cases had likely been silenced as they were in other countries and could emerge now as the debate opens up.