Not legal advice
But here is what I found on Google
Home Alone
In determining whether or not your child can be left home alone, take into consideration your child's maturity level. There is no "legal" age in California in which it is allowable to leave children home alone. Generally, children who are in junior high school are capable of being home by themselves and/or babysitting. If you do leave your children home alone, there are several things you can do to help make sure they are safe:
Tape a list of important phone numbers (your work number, pager number or cell-phone number, your nearest neighbor, relatives, doctor or clinic) on or near the phone. Let your children know when and how they can contact you at work.
Establish emergency procedures, including minor first aid to use in case of accidents. Review these periodically and/or hold practice drills.
Make use of a phone or tape recorder or message board for leaving last-minute instructions or reminders that your children can check when they return from school.
Make a list of productive things your children can do until you arrive home.
Have a nutritious snack ready for them. Agree about the use of cooking appliances and television viewing.
Set guidelines about what your children should do about telephone calls or strangers coming to the door. Practice with them how they might respond.
Discuss the rules for playing and playmates. Children need companionship but they also need some rules to guide them.