Unfortunately, this selection misses (most?) children who may not be well suited to "school maths" - for whatever reason. But these children may succeed just as well in "higher mathematics".
Two anecdotes: (1) June Huh dropped out of high school and stagnated for 6 years in university. In his 6th year, he ran into the fields medal Heisuke Hironaka. It was only then his "slow thinking" and deep creative insight (perhaps the things that hindered him in "school maths" type courses?) proved to be fruitful in higher mathematics. June Huh now has a fields medal.
(https://www.quantamagazine.org/june-huh-high-school-dropout-...)
(2) I was frequently in trouble at school and underachieved relative to my predicted grades. I resented the route learning and arbitrariness of "school mathematics". Due to some miracle I'm currently working towards a PhD in theoretical physics, in the mathematics department of a top university, and I also spend about 90% of my free time working through various advanced maths textbooks for fun. Turns out I'm quite suited for thinking about higher mathematics, despite not being particularly well disposed for school. If my school experience was different, I probably would have done a PhD in pure mathematics instead.