There is no other way to improve much without playing games. If you know all the tactics, know all the opening, know all the endgames, and know all the strategies and positional ideas, but you rarely play, you are at most a theorist and will stay as a beginner. Whether you really know all these things, it's a myth that no one can find out until you begin to play one day.
USCF and FIDE have rating systems. That's how they measure and track your strength. Even all those online chess playing sites have some rating systems which shows your performance. If you don't play, your rating will stay at the default level (looks like nice on paper), but you never improve.
To play and lose every time require some endurance. But if your child perseveres through such trial, s/he will be very strong mentally, even if not chess-wise. I once challenged my student to lose 100 games straight on chesskid.com. But he could not do it. The losing stream stopped at 40-some game, and turned around. Now he is winning much more than losing.