Lawrence Kohlberg's stages of moral development range from level 1 to 6. They increase in order from "obedience" to "individualism and exchange" to "interpersonal relationships" to "social order" to "the social contract" to "universal principles." The stages are meant to be invariant--one must first reach stage 2 before moving on to stage 3, and he found that older children were more likely to be at higher stages.
In evolutionary biology there is a movement to stop calling certain species "higher" than others just because they have more base pairs or divergence from common ancestors. I wonder if the same principle can be applied here too. Just because one must pass through stage 2 to reach stage 6, does that mean that stage 6 is more moral in some objective sense? What does it matter that older children are more likely to rate at higher levels? Judge for yourself, but I've yet to be sold on Kantian universalization.