What realization did piaget have while testing children's iqs?

While testing children's IQs Piaget made the realization that children of a similar age respond to questions similarly.

Children generally had the same incorrect answers. Because of this Piaget determined that teaching needed to be focused to their method of reasoning. When he observed that many of the children were answering the questions with the same wrong answers, he was able to postulate that if education focused more on individual student needs, children may be able to learn better.