You will find that the early education center promises that you will cultivate your children's intelligence by signing up for classes. This abstract commitment can't evaluate the effect at all.
However, the goals of kindergarten semester are, for example, knowing 200 words, reciting 10 stories, using scissors, knowing eight-step origami, and walking smoothly across a 20 cm wide balance beam ... this is called a quantifiable goal.
By the end of the semester, if the child's goal achievement rate reaches 95%, we will say it is useful, and if the goal achievement rate is very low, we will say it is useless.