Legal?

(Impromptu class discussion on friendship)
Student #1:  "The only way to get to know someone is to get drunk with them."
Student #2:  "Exactly."
(silence)
Me:  "Except that no student in this room is 21, so none of you have had a drink before."
(silence)
Student #2:  "Riiiiiight."
(silence)
Student #1:  "We are all 21 on the weekends." 
(silence)

(Impromptu class discussion on underage drinking)