Only with a special license from the state. I had one when I was in HS. I delivered for a combo grocery/store. I had to go to Newark, fill out an application, be fingerprinted, and have my picture taken. I had to have the license on me at all times.
You can work in an establishment under 21.
There shouldn't even be a drinking age. Let alone setting it at 21. Should legalize most drugs too. We are raising veal in this country and everybody from helicopter parents to the government are conspiring in it.
I'm surprised you have not offered a pro tip. Underage students should have 21 year old hookers transport their booze and blow into the alley. Problem solved.