I can speak from personal experience there, for myself, or for students. I've worked with students from when they were complete beginners all the way to master,

I can speak from personal experience there, for myself, or for students. I've worked with students from when they were complete beginners all the way to master, and they were still very much amateurs (with 'amateur brain') at the beginning. And in fact while you can kind of get some vague impressions, you can't really tell who's going to excel. Famously, Mikhail Botvinnik (a world champion seen as the 'patriarch' of the Soviet Chess school) chided a young Anatoly Karpov who showed up to one of his chess schools, "The boy doesn't have a clue about Chess, and there's no future at all for him in this profession." Anatoly Karpov would go on to be one of the most dominant world champions of all time. Even Magnus Carlsen - he is arguably the strongest player of all time and had one of the most meteoric rises to the top. Yet he was at one time rated 900. A year later, with world class coaching and living and breathing chess, he made extremely rapid progress (to about 1900) yet that's still very far from master class.