My oldest grandson started racing in go karts, under the tutelege of my son (his uncle Pat). They added quarter midgets and that gradually ended the kart racing. A win at a Dirt Grand, combined with my grandson reaching his teen years prompted my son to move him to POWRi 600 micro-sprints. Now in his second full season of micros, he is running in the top 10 in points, and is "learning to race" fast open-wheel cars on dirt tracks such as Tri State at Haubstadt, Macon, Jacksonville, and Peoria.
I would guess that both karts and QMs were very good learning grounds, but the QM route is where his "sponsors" began to really notice that we were all "digging deeper" with every move up to another class