I am a high school student and some of this stuff is really helpful (and fun) for studying! It would be really cool to have an avatar for a teenager or adult and has a a more advanced view into some aspects (endocrine system, more advances muscular system with action of muscle tissue, reproductive system including fertilization, gestation, and parturition , etc).
Even for the version for children, I think it would be awesome to include the basic model of a cell and the structures contained within it.
It would also be great to delve deeper into the nervous system and show a neuron and how neurons interact with one another (neurotransmitters, myelination, etc).
Finally, I think an in app purchase about the reproductive system should be added in (though it should be an option, allowing parents to decide whether or not it is appropriate for their child). This could assist parents with children at the cusp of puberty teach their children about the changes your body goes through, menstruation, and learning more about themselves in general to avoid the negative effects of the media teaching children about their bodies, etc.
Great app! Fun and informative!