Issue of over age children in earlier classes

According to latest ASER , appropriate age / class is still a major issue.

18% of children aged 9 are either in grade 1 or 2 (several years behind their age).

At multiple ages, children are not in the grade they should be:

By age 10–12, a noticeable share is still stuck in early or middle grades
Even at age 14–16, many are not yet in secondary school (Class 9–10)
Some students appear to stall or slow down as they move through the system

This points to:

Grade repetition
Late school entry
Temporary dropouts and re-entry
Learning gaps forcing slower progression