Statiscal information

Your explanation was pretty clear right up to that last paragraph (long explanation). It describes something different than what you are saying in the list of four things you need.

Total number of females =COUNTIF(A:A,"f")
Total number of males =COUNTIF(A:A,"M")
Total number of over 12s =SUM(C:C)
Total number of under 12s =SUM(B:B)

Because those answers are so simple, maybe your description of those four items is not detailed enough.

Can you explain what the 3 different attendance columns mean? Does each row correspond to a single person, or some aggregation?

Do you want to know something like: the total number of attendances for rows that are both female and under 12, and that number for each row is the total of the three attendance columns?