Allegations range from a teacher showing pornography to children to a teacher kissing a student.
The Commission on Teacher Credentialing had a three year backlog totaling more than 12,000 cases in 2009.
State auditor Elaine Howle said those delays allowed teachers of questionable character to stay in their jobs. The audit was released Thursday in Sacramento.
The commission, which has 32 full-time employees, voted last year to revoke the credentials of 306 teachers and administrators.
The Associated Press contributed to this story