The Classroom Key is one of the keys Harry Mason picks up in Silent Hill. The key can be found in the Otherworld version of Midwich Elementary School. It can only be picked up after Harry finds the rubber ball. The key is resting in one of the drainage pipes on the roof and needs to be flushed out by means of turning on a water reserve. The problem lies with another drain carrying the water away from the drain where the key lay. It must be plugged with the rubber ball, allowing the water to wash the key down the drain-pipe. Harry can find it on the ground in the school courtyard.
The key unlocks the door to the northwest classroom on the second floor of the school, allowing the player to progress with the story.