First of all, in theory,
1. Strength is roughly divided into three parts: arms, waist and abdomen, and legs (it is worth noting that most climbing processes rely on waist and abdomen strength, not just arms);
Coordination mainly refers to the cooperation between hands and feet, which can be trained by skipping rope;
Flexibility is more about practicing ligaments, which can be found in online professional tutorials.
2. Second, practice on the spot. Personally, I think bouldering is the most effective method. Almost all rock climbing gyms have bouldering grounds, and the difficulty is divided according to different routes.
3. If you have the conditions, you can also take your children to try the natural rock wall. If you are an amateur, you must have professional protection.
From that point of view of train children
I don't know the age of my child. If I am young, it can be used as entertainment. At the same time, I encourage my children to try. After all, children will definitely be scared and have enough experience. If you are a teenager and ta is interested in this sport, you can make a general training plan from the perspective of sports: strength training, venue training, diet and catering, etc. There are also many foreign rock climbing tutorials taken quite early on the Internet, which can be used for reference.
If P.S. develops in a professional direction, children can go to physical education institutes if they are very willing, and many of them have rock climbing majors.