"A general rule of thumb is that kids under age seven
aren't capable of thinking logically and putting cause and effect together," Tanner said. "They are reliant on caregivers to structure their day." Children between ages 7
years aren't generally ready to self-supervise for an extended period, but in a routine and predictable environment, such as just after school, they can manage, Tanner said. Children 12 and 13 years old should be judged on a case- by-case basis but should not be left alone overnight.
Contact Child Welfare Information Gateway at 800-394-3366,
and the staff there will refer you to your local child protective services agency to learn about age guidelines in your area.
The provided link may also help you. Age Restrictions For Latchkey kids