The BA is relative to the competition the player is playing agaginst---how tough is the league?
Is it a "soft" league" ?
What is the pitching like in the league?
For me .300 at the HS level is not a good thing. I like to see a kid increase his BA every year against the same competition in HS--that tells me more than just the BA--this shows that the player is improving
As for comparisons w you can only compare BA's if they are playing against the same competition otherwise I think you are just spinning your wheels