Did you apply yourself equally at both? Without making any assumptions, many people do sail through college hardly putting enough effort. If people half-assed startups the same way, starting work on the prototype two days before an investor pitch, say, that wouldn't be much of a learning experience either.

In your own startup, it feels like every stroke counts, and you are doing something you find exciting and meaningful. It's likely not that startups offer more teaching experience, it's just that you're bound to get more out of something you really dive into.

Having said that, most (all?) college curricula do not cater for people intending to do startups, but they still have a lot to offer.