The San Diego Unified School District looks closely at its employees.The district uses background checks, fingerprinting, tuberculosis tests for its employees or prospective employees.For volunteers, 10News has learned the policies are much looser."The policy is old. It's something we need to address. We do not require background checks, but we need a discussion with the principals to decide, given state of things today, at what point do we require background checks?" said Jack Brandais of the San Diego Unified School District.Vincent Greco is facing criminal charges for not registering as a sex offender after a complaint, thus casting a shadow over the school where he volunteered.Brandais said Greco was supervised almost all of the time, but the system wasn't foolproof."We try not to have volunteers having full charge of students at any time," said Brandais.Now another arrest of a person entrusted with children has parents upset.One parent told 10News, "They have to screen everybody. You don't know who to trust anymore ...""The staff at SCPA (School of Creative and Performing Arts) ... they are shattered over this," said Jim Esterbrooks of the County Office of Education.The County Office of Education has guidelines for volunteers, including one that states: "It is recommended that school districts require Level 1 volunteers to have a Megan's Law check."And guests have to sign this: "It is possible that I may have more than occasional or infrequent contact with students. Under penal Code, I am required to disclose to school officials if I am a registered sex offender. Failure could result in arrest, prosecution and imprisonment."There are guidelines, not requirements."Some districts go further, others not as far. But in each district's case, nothing is more important than student safety," said Esterbrooks.The Sweetwater Union High School District's volunteer screening has each volunteer required to fill out an application. Long-term volunteers -- those who work one or more hours regularly over a one-month or longer period of time and who are in direct contact with students -- shall be fingerprinted and given a tuberculosis test.The volunteer checklist for the Oceanside Unified School District is an information sheet that requires a first and last name, Social Security number and a request for a photo ID. The individual must then receive stand and federal fingerprint clearance.