Which keyboard should I buy for a young child?

This is the question I get asked more than any other, usually a week or two before a child’s first lesson, and usually by a parent standing in a shop feeling slightly out of their depth.
The short answer: you need fewer things than the shop will tell you, and one thing the shop may not mention at all.
Touch-sensitive keys matter more than anything else. If pressing harder doesn’t make a louder sound, your child cannot learn to play expressively - and they will find a real piano strange when they meet one.
Full-size keys. Small keys teach small hand shapes that have to be unlearned later.
Sixty-one keys is enough to start. Eighty-eight is lovely, but it is not the thing to spend the money on first.
What doesn’t matter: hundreds of built-in voices, backing rhythms, flashing lights above the keys. None of it has ever helped a student of mine progress, and the lights in particular tend to teach children to watch instead of listen.
