If you want to measure your child's physical development, just compare what they can do on your home swing set.
I remember when Christina was in the baby swing, and couldn't climb the ladder.
It gives her such a sense of accomplishment to have mastered all the equipment. You can see her determination as she climbs the ladder, and smile of pride as she swings all by herself. The problem is, now she wants to swing on the trapeze, and jump off! Yikes!