Many people have grit, not all of them are successful. Some people don't have grit yet are still successful.

So obviously grit isn't the unifying thing that leads to success.

High Schools and Universities are by no metrics a measurement for success. And if you want to make them that you can start with the luck of whether you are born with rich parents or poor parents.

Of course grit is good to have, but it's not what define success.