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Many parents are worried and upset, even those parents whose children never had Beltran as a teacher.
Beltran is being held in jail on $1 million bail. Santa Monica police say he's accused of committing lewd acts with students during school hours.
As students prepare for testing day, the teachers and staff at Lincoln Middle School are trying to keep the kids focused. But the shocking arrest of one of the most popular teachers at the school has the district, teachers, and parents in a state of disbelief.
Beltran is accused of molesting four seventh grade girls.
"It's frightening for our children and it's frightening for our parents, but I think that the staff response has been amazing," said parent Rebecca Kennerly.
Extra counselors are on hand Monday for any students who need to talk.
Islvana Flores tried to ease her daughter's concerns before first period.
"She's kind of nervous but she's fine, I think the school is safe," said Flores. "You know, they have everything in control. So I think everything is fine."
Santa Monica police arrested Beltran on Saturday after a 12-year-old girl told her parents she'd been repeatedly abused. Police interviewed other students and say they have identified three more victims. Investigators say in at least one case, the alleged abuse lasted more than a year.
Authorities aren't saying what lewd acts allegedly occurred, but police say they took place during school hours.
Beltran has taught English as a second language at the school for two decades. He's worked in the Santa Monica-Malibu Unified School District for 30 years. He's respected by his peers and has hosted a cultural feast every year.
"Students would come together, they'd write recipes, bring their home recipes to share with the entire community as an exercise for them to be able to translate their home experiences to English to help them learn the language," said Principal Tristan Komlos.
Principal Komlos says the teachers are stunned and trying to avoid jumping to conclusions.
Some parents who don't know Beltran say the allegations have caused them to lose confidence in the school's ability to keep kids safe.
"It's what's going on in the classrooms, how are we checking the teachers? Who's watching them? Why are they alone, allegedly if this happened, why are you alone with a 12-year-old girl? I'm very upset," said parent Lisette Bauersachs.
Police want to know if any other students may have been victimized before the case against Beltran is presented to the district attorney's office. If you have any information, you're asked to call the Santa Monica Police Department at (310) 458-8491.
School officials say attendance is down Monday, but they want to assure parents that they are doing everything they can to help the students during this time.
Eyewitness News reporters Melissa MacBride and Jovana Lara contributed to this report.