Thanks. Right now he's using Typing Club, a typing tutor for kids. I will probably have him finish the sequence on there (or at least get to 20wpm on the lower case keys) before moving on to gtypist, keybr or nitrotype.

He only does 2-3 mins per day of focused typing practice. Most of his daily non-school study time is spent on math (Math Academy), Chinese (writing) and memorizing essential root words (using Anki). I don't want to add anything, as he already has little free time to play and read on weekdays.