Not sure what the answer is, as someone will always find a way to get a head start...?
Tapping up young players has been going on since the start of the professional game and before Football Agents even existed... and there have always been inducements.
Denis Law spoke of when he signed as a teenager for Huddersfield & his Dad was made a paid club scout... His Dad was an Aberdeen Trawlerman who rarely set foot on land.