Additional-- even the worst Caltech undergrads were reasonably smart and dedicated. My recollection is Caltech had a 33% non-matriculation rate--extremely high for a top-select school
I won a statewide competition in chemistry in high school, went to Caltech as an undergraduate, and it was hard. Transferred to another top-rated school, which wasn't nearly as hard.
To get a Caltech degree does require being smart, and being dedicated.