Mixed-age groups of home-schooled kids (e.g., at co-op events) tend to just play, with the older ones typically watching out for the younger kids, whether they are siblings or not.

Mixed-age groups of formally-schooled kids begin by setting up a hierarchy that usually depends on grade in school* and then is continually refined.

* H-S kids in a mixed group are immediately marked as outsiders by this question. They either don't know or operate at different levels in different subjects.

Depends on how studious you are.