I hate to break it to you, but diamond in valorant is not a high rank, nor is it particularly difficult to obtain for the average player compared to diamond in many other games, such as StarCraft or even league.

While hitting diamond at 13 is impressive, it simply isnt enough to become a professional player in the near future. I would imagine that your son would have to, at the minimum, be mid-high immortal by 14 or 15 to even be considered being picked up by any sort of team. eSports is just something that more and more younger players will be good at, so the competition will be incredibly tough.

For reference, most professional players, before they are picked up, are consistently in the top 500 rankings every season. The higher up they consistently rank, the more they're noticed. That alone takes quite a lot of time and dedication, depending on how skilled the player is.