Real simple - a player draws 2 cards. If the cards are "connected" (ex: H, I or P,Q), the player keeps the pair. If the pairs aren't "adjacent" (ex: B, R), they turn the cards back over and the next person draws.
A can be paired with Z. When the only cards left are ones that can't be paired, the game is over, and the student with the most pairs wins. (*Note: If the children were having difficulty - some were even singing the alphabet song - I gave them a simple chart to help.)