A former teacher in the Los Angeles Unified School District has been arrested on suspicion of committing lewd acts and sexually abusing 20 children and an adult, The Los Angeles Times says. Robert Pimentel, 57, taught at George de la Torre Jr. Elementary School in Wilmington, Calif. Police began an investigation in March after several fourth-grade girls said they had been inappropriately touched.The charges against Pimentel involve sexual abuse and lewd acts on a child and cover the period from September 2011 to March 2012.