Way back when I was in fourth grade I was taught to type on a manual Royal typewriter with blank keys, which was a bit disorienting to say the least. At the time it seemed like just another instance of a teacher torturing a student, but it worked. It was slow going at first, but the blank keys succeeded in getting me to mentally map the characters and stop looking at the keys. There are some who think that you should take sandpaper in hand and grind the letters from keyboards for typing instruction.
I like a crafts project as much as the next guy but this seems like too much pain for too little gain, particularly when you have to do a classroom with 30 keyboards. The Das Keyboard Ultimate comes without the letters on the keys, and has a two-port USB hub built in. It’s available at ThinkGeek but at $130, it costs about five-times as much as a standard USB keyboard with all the numbers and letters in place.
Why not just cover the keys for typing class? That’s the idea behind SpeedSkin rubber overlays. The sheet covers each key, hiding its letter, symbol or number. At $10, it’s much more reasonable, and it allows a room of computers to be used for typing class in period 3 and as a computer lab in period 4. The keyboard covers have bumps for finger positioning and the function keys remain visible, but SpeedSkin works on external keyboards and select notebooks.