What is so unbelievably frustrating about math education is that these interesting questions are not even hinted at until far, far down the line (and before people make the assumption I was educated outside the US).
I avoided math like the plague until my PhD program. Real analysis was a program requirement so I had to quickly teach myself calculus and get up to speed—and I found I really, really liked it. These high level questions are just so interesting and beyond the rote calculation I thought math was.
I hope I can give my daughter a glimpse of the interesting parts before the school system manages to kill her interest altogether (and I would welcome tips to that end if anyone has them).
Geometric proofs are really accessible. You don't need any algebra to prove Pythagoras' theorem, or that the sum of the inner angles of a triangle is 180 degrees, for example. Compass and straight-edge construction of simple figures is also fun.
Reminds me of "A Mathematician's Lament" [0]. I'd prefer to link a non-PDF copy, but nothing came up with a casual search.
[0] https://en.wikipedia.org/wiki/A_Mathematician's_Lament