Babysitter - Now Hiring

We are looking for a great babysitter for 3 children in San Francisco. We would prefer someone who could help out with homework help. We would prefer a babysitter who has their own car, who does not smoke, who is CPR certified and who has college degree. We have a full time nanny, but are looking for help on weekends or evenings when she is not available or when she is on vacation.