Pitc, high/scope, the creative curriculum for infants and toddlers, and reggio emilia all emphasize:

I believe the answer is: children's capabilities as active learners

Until we enter adulthood, our brain will keep developing and keep unlocking new cognitive abilities that we can use to survive in our environment.

Pitc, high/scope, the creative curriculum for infants and toddlers, and reggio emilia are filled with tests to measure whether the children are experiencing proper development if compared to other children in their age group.