Until the current OIA Ad's move along in life [those that still remember the ILH and OIA going their separate ways] you will forever have this problem.  It's really too bad.  Private schools have always recruited, Public schools use "G.E" to get players or other talented, influenced, academically or musically inclined students to come to their campus. That is how certain schools can go to the DOE and ask for more money when their campus' get over crowded and have too many students.
It's how the administration [principals, vice principals] moves up the DOE chain of command by them saying they ran a "big school".
Adding to what barak181 said--what if the smaller schools in the OIA get fed up with being beaten up  week after week that they form their own "D-II" league with the smaller ILH schools.  That would leave the big boys all alone as well.
Let's just hope it does not come to that.  
OIA..learn to get along with others..life is full of compromise.