@ricck1,
“There are many students with mediocre grades and scores at Harvard.”
First, it depends on what means by “mediocre.” If by mediocre one means average, well, the average SAT in the US is something around 1550 or a little less. I doubt there ae “many” students at Harvard with an SAT of 1550. I wouldn’t be at all surprised if there aren’t any. Even if one interprets mediocre as plus or minus a standard deviations, that’s an SAT score in the low-to-mid-1800s. There aren’t many Harvard students with SATs that low. There are a few, but not many.
Ditto on grades, although it’s a little tougher to define mediocre or average when it comes to GPA.
There aren’t many at all. Check out Harvard’s Common Data Set, or the the Crimson’s survey on incoming freshmen. There are few folks with mediocre grades and scores.