$6.50 seems low, there should be a casual loading on top of that. Of about 1.23 or 1.25 depending on the state/agreement.

I work with some Fast food awards, don't think I have ever come across an employee who is under the age of 15. The main franchise I deal with is pretty consistent across the stores, across the states with what they pay.
The ages are a percentage of the adult wage. Basically reduce by 10% for every year under 21yo.