I am not convinced „doing hard things“ should be a top priority for kids. For my own kids -or actually everyone- i hope they find a passion big enough to make a living. This takes time and lots of experimenting and cannot be forced into existance. Grinding through „hard things“ can leave you with a great deal of confusion. It is so much easier to do „hard things“ if you love doing them. The problem with math is: it is very hard to learn later on in life. Maybe even as hard as drawing. Schools should really focus on reading, drawing, writing and math- everything else should come secondary.