I'll try to be clearer. When they're in the simulation, they don't have any memory of entering it. However, before each simulation, the students show up in the Battle Simulation room and are given a brief explanation of how it works if they we're there since day one. Once they're out of the simulations, they immediately remember going into the classroom and preparing to get plugged in. Once they get out, it's not a surprise to them, and it's not like they've been tricked. They knew beforehand that what they're about to experience is fake, they just don't know during it.