A Los Angeles teacher was arrested allegedly molesting 20 of his students. The teacher, Robert Pimentel, was working for close to four decades in the Los Angeles Unified School District, and this latest arrest is just one of several high-profile sexual abuse cases involving L.A. teachers within two years.

The Los Angeles Police Department announced the arrest on Wednesday. The Juvenile Division’s Sexually Exploited Child Unit had been investigating the case since March 18, 2012. Robert Pimentel was a fourth-grade teacher at George De La Torre Jr. Elementary School, located in the Los Angeles district of Wilimington, and the case was brought to the attention of the LAPD after several girls told their parents that Pimentel had inappropriately touched them.

Pimentel had left George De La Torre Jr. Elementary School around the same time police began their investigation once the allegations were brought up and reported to the police. Pimental had been an employee of the LAUSD since 1974, and the case involved 20 victims, 19 children and one adult.

Pimentel was charged with eight counts of continuous sexual abuse and seven counts of lewd acts upon a child. Pimentel was arrested on Wednesday, and his bail was set at $12 million. The Associated Press reports that Pimentel could also be charged with several misdemeanors stemming from the alleged molestation.

John Deasy, LAUSD superintendent, told the AP that the school’s principal was also fired due to the poor handling of the alleged sexual abuse by Pimentel once the allegations were reported. The Los Angeles Times reports that the alleged molestation occurred between September 2011 and March 2012.

The United Teachers of Los Angeles issued a statement following the news of Pimentel’s arrest.

“We do know the individual resigned and that he is no longer a member of UTLA," the teacher's union said. "The union will not be involved in his defense. The allegations described are horrific. As teachers, we have a duty to uphold the trust our students and their parents place in us.”

The LAUSD has been facing intense scrutiny following several sex abuse cases involving L.A. teachers. Last February, Mark Berndt, a teacher at Miramonte Elementary School, was arrested and charged with 23 counts of performing lewd acts on more than 23 children. Berndt would photograph the abuse and play sex games with the children, according to an earlier AP report. The abuse occurred over the course of two years, between 2008 and 2010.

In 2010, Berndt dropped off film to be developed at a local CVS, and, when the employees saw pictures of children bound, gagged and blindfolded, they reported it to the police. Some of the acts included Berndt feeding the children cookies that had his semen on it and putting cockroaches on the faces of children who were blindfolded, reports the AP. Berndt pleaded not guilty and is currently awaiting trial.

The AP reports of a $6.9 million settlement, to be paid by the LAUSD, in December to a boy who had been molested. The L.A. Times also reports that an audit of the LAUSD, released in November 2012, discovered 150 sexual abuse allegations that had not been reported to the police.