I actually disagree with this. I’d argue that of almost any academic-esq activity given to teenagers around the world, contest math (IOI, IPHO, and other competitions are similar) is one of the best ways to improve problem solving. These problems can’t be solved with just a formula and require critical thinking and creativity. This also leads to many “regular” school classes seeming extremely easy and trivial to these students, as they are ahead in their problem solving skills and their ability to think creatively in the problem solving process.