Both my folks were teachers when I was growing up (my mom AT my high school) so I have a lot of respect for the challenges they face. Seems that in a situation like this (particularly if you embraced the above mentioned common sense and perspective) it would be fairly easy to take lemons and make lemonade so to speak... ESPECIALLY since the teacher/school was confronted with not simply one kid doing something he shouldn't, but a classroom of 19 dazed and confused pupils:

"It's become readily apparent that most all of you are, well... fully baked, much like the brownies you all shared. So put down your books, we're going to go on a field trip. First stop, the park by the library, so we can meet some shining examples of what will happen to you eventually if you should decide to do this EVERY day. Then, we'll stop at central park where you can all buy 1 or 2 or 20 burritos as I'm sure all of you will be quite hungry by then... last stop, Castillo's where we'll pick up 20 gallons of paint and the same amount of brushes. Then, every day for the next month, rather than going home after school, you will get to help beautify the school and neighborhood until it's time to go home for your dinner. You will NOT get a break at 4:20. All of your parents have already been notified."