It’s really difficult to say because we can’t put the same student in both places.
So much depends upon the student. We’re “average” or slightly above at our school, so our top kids tend to max out what can be done, but the bar is lower than at other schools even if GPA matches. These kids get into their freshman classes and like all humans, compare themselves to the others. Some will buckle down and fill in gaps, eagerly taking in the new information but others will feel they’re overwhelmed, head to a party to “destress” telling themselves they’ll study later and later doesn’t actually come or they’re lost when it does because there are gaps to fill. Then there are all the students in between the two on the ends.
I ended up telling students I knew about my theory and encouraging them to find gaps and make time to fill them in quickly rather than assuming they weren’t as smart as their peers. It worked for at least a few who came back to thank me for warning them.
I have not found that curriculums are as similar as people say they are. Sort of, yes, but top schools put far more challenge into their tests and classes. My youngest son called his CC Bio 101 college class, “Bio-Lite” after he sat in on his brother’s at a Top Research U. I asked him the difference. He said something to the effect of (numbers might be off, concept isn’t): “In my class we learned, ‘There’s an enzyme that helps with the process.’ In my brother’s class they were learning about 12 different enzymes, by name, and what each did.” Both were Bio 101 classes designed to be taken by Freshmen. The first would have been an AP substitute. The other assumed kids had already completed an AP level class.
I can’t comment on CS though. I know far more about math/science since that’s my specialty and often what kids return to talk about. When they had them to share, seeing tests from different schools was rather eye-opening.