> I teach my beginning students simple openings like the London System as white
This is not a good idea for a number of reasons. One is a d4 opening will lead to a more closed game, at which the beginner is at a disadvantage, since it requires a deeper understanding of positioning and strategy.
Two is the beginner will learn less if playing closed games initially. A beginner should aim for open games (1. e4) where they will have more opportunity to learn tactics. As they advance, they can move to closed game (1. d4) strategy.
Inevitably, you will play as black and some of your opponents will open with 1. d4. So you will be learning a little about closed games from the beginning even if you're never opening with them yourself.
One thing I did initially was just to usually play the same opening moves. As white, I always played 1. e4. As black, I would see what piece white moved, and then played the same response to that every time. This cut down on the openings I had to learn - at the end of move 1, the board was always in one of twenty positions, as opposed to one of forty positions, or one of sixty positions. Easy alpha-beta pruning.
For example, I never played the Italian Game as white. If white played it, I might play the Rousseau Gambit, which is probably not good against experts, but is good enough against beginners who depend on knowing the traps of the Italian Game. Even if they do 4. d4, you can do 4...fxe4 and then the board is wide open again, even if you're at a slight positional disadvantage.
This is not a good idea for a number of reasons. One is a d4 opening will lead to a more closed game, at which the beginner is at a disadvantage, since it requires a deeper understanding of positioning and strategy.
Two is the beginner will learn less if playing closed games initially. A beginner should aim for open games (1. e4) where they will have more opportunity to learn tactics. As they advance, they can move to closed game (1. d4) strategy.
Inevitably, you will play as black and some of your opponents will open with 1. d4. So you will be learning a little about closed games from the beginning even if you're never opening with them yourself.
One thing I did initially was just to usually play the same opening moves. As white, I always played 1. e4. As black, I would see what piece white moved, and then played the same response to that every time. This cut down on the openings I had to learn - at the end of move 1, the board was always in one of twenty positions, as opposed to one of forty positions, or one of sixty positions. Easy alpha-beta pruning.
For example, I never played the Italian Game as white. If white played it, I might play the Rousseau Gambit, which is probably not good against experts, but is good enough against beginners who depend on knowing the traps of the Italian Game. Even if they do 4. d4, you can do 4...fxe4 and then the board is wide open again, even if you're at a slight positional disadvantage.