I do agree about the maturation rate vs past times. But, I would chalk this up to a number of other factors which have changed and have had a more outsized impact than schools.

For one, parenting is far different, with parents now more integrally involved in their childrens' day to day lives. Kids are not encouraged to be independent, nor do they have as much opportunity to make decisions for themselves.

I would imagine "Coddling" speaks to that as well. But, that really has very little to do with schools.