I would suggest approaching this in two structured phases - "breadth" and "depth". In the breadth phase, you instruct the kid to study the topic of interest at

I would suggest approaching this in two structured phases - "breadth" and "depth". In the breadth phase, you instruct the kid to study the topic of interest at a distance, collect information, attend events casually and give some reports explaining what they like. Make the thing of "pursuing an interest" just a little bit academic and intentional on their part. With a lot of topics they'll have their fill and loosen their grip pretty quickly, and when that happens, allow them to go on to the next thing. If they can't shut up about it, that's when you go towards the depth phase and push them towards a more intensive effort, to take the class, read the book, join the club. Set modest goals that still take a committment, and indicate that it's very likely that some kids will be ahead or pick up the material faster. They should still report how things go and get your feedback so that you can spot issues, or teach them how to seek out good feedback where you lack competence. But there's a definite thing here of getting them to see the struggle itself as something rewarding, not the outcome like "being the best" or "making a career". Because if they get a feel for that, they will reach adulthood with some sense of balance and intention to what they pursue and why and a sense of their strengths and weaknesses.