My kids were using the flashforge at 7 years old and making their own models in 123d sculpt. It's not something they would just go and do, because they know it's daddy's machine, so they have always had adult supervision. I just do the hard stuff, bed levelling etc for them.

My eldest just turned 9, and I built her a purple kossel mini, and am building a bright pink one for my youngest daughter. By the time my kids get to high school, I want them to be way ahead of the class. This isn't a technology fad after all. I only wish it existed when I was back at school in the 80's because X/Y felt tip pen plotters were no where near as interesting!

the Kossel is a great build for kids, no heat bed (by default) low power consumption, quick build time, Zprobe so no bed levelling really to do.. they are such a great design.