Most all low-wing airplanes are more aerobatic than high wing trainers and faster as well but this is not necessarily a cause-and-effect relationship. You can kit bash a trainer into a low wing design by putting the wing on the bottom of the fusilage but it will still fly slow. Fly your trainer inverted and suddenly you are flying a low wing airplane with anhedral instead of dihedral but is still flys slow.
Indeed, nothing prevents a high wing design from being fast or aerobatic. A lot of quickie-500 racing planes are high wing and they aren't for beginners. The Ultra Stik is also a very aerobatic airplane.