stuff I've noticed (feel free to correct me):
1. max age of tutee is 21, once he turns 22, he can't be tutored anymore. minimum age of tutor is 24. so from 22-23, he can't be tutored. you might want to send him on loan intstead.
2. determined or outspoken players are more difficult to talk to or even convince to be tutored or learn certain ppm. it took me about 10 reload just for Andy Carroll to accept to be tutored by Drogba even if they had the same personalities.
3. from ages 14-17, I train my wonderkids physical stats because this is the time they improve dramatically & work on their weaknesses. from 18-21, I work on their technical skills(depending on their position & role in the team). from 22-23, i send them on loan or put them in the first team(available for reserves).
4. putting a wonderkid in the first team fast tracks their development. I put phil jones straight into my FT & he fulfilled his PA by age 22. even if he made several mistakes led to goal, he learned from it & became a better player.
5. VERY IMPORTANT: if you notice your wonderkids' stats becoming stagnant. talk to him (improve in training). you have to be on his *** if he doesn't show signs of improvement. this will help him achieve his PA! I like to check on players every 15th of the month & see if they have red arrows on their stat sheets, they usually pick up training after I give them a talk, and by the end of the month in the training report, those players don't fail to impress the training coach.
6. I don't really like loaning wonderkids, because you don't get to handle their progress. It's imperative that you keep an eye on their development to reach that PA. I had neymar & paulo henrique with a 4 1/2 star PA, so I put them on the first team straight away. although they did not reach that 4 1/2 PA, they still progressed well to reach 4 stars.