Have the students bring in 2 packets of sugar (or 1/2 bag equal/sweet n low) and 2 ziplock bags (1 sandwich size & 1 freezer size)
Bring in 4 gallons of milk for 90 students, 1 large bottle of vanilla, 1 box of rock salt and a cooler of ice.
Have the students pour the sugar in the sandwich bag while they are waiting.
As they come up to the table or counter, have them put 2 cups of ice and 1 tablespoon of rock salt in the freezer size bag.
Then pour 1 cup of milk and 1 teaspoon of vanilla into the sandwich bag with the sugar.
Seal the small bag and place it inside the large bag.
Seal the large bag and have them shake for about 5 minutes.
Once the inside ingredients begin to firm up they can take it out of the big bag, dispose of it's contents,and eat their ice cream.
They think it is great fun and the ice cream is pretty good.