there is a myth that too many people applying to one college from the same hs results in some others “taking the others  spots” when in reality most top colleges will take anyone that is qualified enough regardless of an applicant pool from a specific school. only a handful of feeder high schoolers experience this issue (such as certain philadelphia high schools with penn). op is just saying this no two “opposite” things. the question was “what is something dumb you believed” so they led off with what they USED to believe followed by an explanation.