No, I have not. But I help some son friends and "my" teaching have "made miracles" for them, switching from "under-performing, unable to understand" to "brillia

No, I have not. But I help some son friends and "my" teaching have "made miracles" for them, switching from "under-performing, unable to understand" to "brilliant". Just interesting them, just showing them practical reasoning and examples and pushing them going further alone. You might like as well a book from a real teacher https://en.wikipedia.org/wiki/A_Mathematician%27s_Lament https://en.wikipedia.org/wiki/A_Mathematician%27s_Lament as a good example of the same concept.