I've introduced more people to D&D than I can count, and almost all of them continue to play to this day!  I've taught many D&D classes here on Outschool, and one thing that I notice in a lot of students is a general sort of confusion over the rules - things that a good Dungeon Master can easily help with and explain during class - but that might make a child nervous to play in a group of peers, where the DM might be less experienced.  I'm a big believer that the best way to learn D&D is to actually play D&D, but I'm also adept at giving clear, simple explanations of the rules.