In late June of 1995, Snape reveals his dark mark to Cornelius Fudge. He takes in a special mission for the order. Snape is a spy for Dumbledore. Harry finds out that Snape is a member of the order when he arrives at 12 grimmauld place to give a report. He is not a real death eater at this point just a spy for Dumbledore and the order. On the 2nd of September in 1995 he teaches Draught of Peace in potions class.