There is a level of maturity that comes through aging+life experience.
The average 16 year old has problems acting like an adult and dealing with customers in a professional manner.
If you sat and looked closely at how 11yr old kids act compared to 16 yr olds you'll see a big difference in confidence, ability to understand procedure and the reasons why they are followed.
Not trying to be horrible but as an 11yr old you still rely on your parents to a large degree to tell you what to do from one step to the next.
I would hate to let you get in to a situation where you had a irate customer approached you. I feel that you'd crumble and we'd have an even bigger problem other than the customer.
And yes there is a social reponsability that goes with the territory.
11yr ols kids should be "KIDS" having fun, making friends, going to SCHOOL and all the things that make kid what they are.
Don't be in such a hurry to grow up.
Society would look sideways at any restaurant that would hire minors.
When you're 16 get down to the BK and sign up. But until then value your time as a young person and have fun. Your time will come soon enough when you have to get a job.