Count Of Names By Date Of Birth (DOB)

I am using Office 2007 - Excel

I have a list of students with associated Schools
For each High School -Based on students Date of Birth (DOB) I am trying to get a count for:
Students UNDER 16 DOB before 8/25/91 and for each high school students over 16 DOB after 8/25/91

I thought subtototals, countif , maybe a pivot table to break down by school then do the 2 counts -
but I am at a loss for a formula to do the count

I have attached a sample file but the actual file has thousands of students and 23 different High schools which is why I was trying for subtotals or Pivot