Parse the question more closely:

Has [early] Scratch [experience] [led to] [fulfilling] [careers]?

All those modifiers create so much leeway that answering the question can be no more than a parlor game. How early? What kind of experience? By led, do we mean direct causality? What is fulfilling? Is a job a career?

Teaching is lighting tinder in various stages of dryness and hoping that it smolders for long enough that you can add fuel to the fire and get something going. In the right environment, it doesn't matter how you light it. Scratch, card games, helping grandma with recipes, does it really matter?