Let’s call it CCHS (College Confidential High School).
What would it be like for you? Get as creative as you can, no limitations 
Half the students would be adults.
Half the adult students would have kids who already graduated from college. But the parents just can’t graduate from CCHS
Kids would brag about attending THE most competitive school in the state/world. Too late, they’d realize that their class rank sucks and MIT only takes the top 10
High rates of depression and substance abuse among guidance counselors
Oops, forgot to mention—the EC to student ratio would be 20:1
EVERYONE would be in the top 1%. The New York Times would feature your school, because the rules of statistics had been changed to accommodate it.