It depends on how your Children data are recorded, but you can do this via summary fields in the Children table. You will need to create a summary field (Count Of, not Total) for each of the variables you want to track. The question is, what to count?
If you have a checkbox field like "Enrolled", you can just count that field. If it's empty, they're not enrolled; if it's checked, they are.
Otherwise, you can add calculation fields to the table that result in a 1 or nothing, depending on the right conditions. For example, if you want to record boys vs. girls, you can have something like this:
boyCount = Case ( Gender = "Male" ; 1 ; "" )
girlCount = Case ( Gender = "Female" ; 1 ; "" )
Then you can do a count on that.