According to the Russian School of Chess: endgame is the most important part of chess, and should be studied as the first subject. The Chinese School of Chess, endgame is considered no less important than the ultra-sanctuary openings.
When we watch beginners play games. Most games end up in checkmate in middle games. But still some end up as one side has a queen or two rooks and another side has a lonely king, the winning side can't make the kill. They move round and round, but have to shake hands in the end. It's very sad to see such a scene.
Not only beginners have difficulty with endgames, but also masters sometimes do. We had the famous game that a WGM could not find a checkmate in NB endgame.
Improving your endgames will greatly improve your winning rate. At 2000 level, at least half of the games end up in endgames. If you could win half of them, your winning rate will at least double.
Many parents think that chess is like other interesting activities, learn it once and reap benefits all your life. Yes, the statement is true, but the benefits could be small or big. If you only want to learn to play chess, yes, a few lessons are enough to learn piece moves and checkmate. You get "chess playing" knowledge. This knowledge is your only benefit.
If you want your child to learn: how to face stronger opponents, how to handle the disappointment after losing, how to be humble after winning, how to think, how to be patient, or how to persist, a few lessons are definitely not enough. It requires years of learning. Learning chess is a step by step, gradual, long term process. It's not a cram for tests. If you push them to learn too much in one session, they will only get a few points and forget everything else. They won't be able to use the knowledge they learn. Practice is much more important in chess than knowledge.
Like math and music, chess requires persistent learning and practicing, almost daily.