A fired Los Angeles Unified School District police officer was sentenced in Pasadena Superior Court to three years in state prison for trying to rape a retarded high school girl. Reuben Gonzalez, 37, could be freed pending appeal if he posts $10,000 bail, Judge Coleman Swart also ruled. Gonzalez, of South Gate, a 12-year veteran of the school district's police force, was convicted in October of attempted rape and sexual battery. Deputy Dist. Atty. James Koller said Gonzalez attacked a 16-year-old girl in a storage room on the campus of Wilson High School in Lincoln Heights Feb. 25.