Hmmm. This is a UK-based site but the timing of your post suggests that you might be in the USA.
First, here are the UK rules:
You can only work if your employer obtains a permit for you from your local education authority. The LEA won't issue a permit if they regard the work as unsuitable. (e.g. you wouldn't get a permit to work in heavy engineering). The LEA can withdraw the permit if the work seems to be affecting your schooling (e.g. if your teachers report that you're falling asleep in class or not doing your homework).
You can't work before 7.00am or after 7.00pm. On school days you can't work for more than 1 hour before school or for more than 2 hours in total.
On Saturdays you can't work for more than 5 hours. On Sundays you can't work for more than 2 hours. During term time, you can't work more than 12 hours in any one week.
During school holidays, the maximum number of hours goes up to 25 per week. You can work up to 5 hours per day, except Sundays (when you can only work for 2 hours).
If you need the rules in the USA (which might vary from state to state), you should try posting on this site:
http://answers.yahoo.com/
or this one:
http://www.answerbag.com/
(NB: Remember to say which state you're in).
Chris