I keep the book for my son's HS team and I don't pad the stats, I assure you.
We had a pretty good season, and we are deep in pitching. We had a .357 avg. as a team. Our opponents were held to .253 against us. So we had several guys hit over the team average, but then again, those guys were all first or second team All District, too.
Because we were a top team, we alway saw the other teams' best pitchers. Often, our opponents would thus see the other teams' lesser pitchers, then run into us. On the other hand, our own guys never had to bat against our own pitchers, which was something of an advantage.
Generally, in our district, I think someone hitting .250 is unlikely to play much. In the .300-.350 range, you can play but will bat in the lower half. In the .350-.400 range, you are in the top half of the lineup. Above .400, you are a stud and likely college level player. No more than 3 guys out of 7 teams hit an honest .450+.
Anyone claiming to hit over .500 in our district plays for a team that doesn't keep an honest scorebook, IMHO. This area is too deep in top pitchers and I haven't seen anyone get to .500 for a full season in some time.
There are districts in the area where you might see some higher averages. One district in particular has 4-5 top teams, but also 3 hapless teams and thus, you get to feast on weak pitching and weak fielding for 6 of your 20 games. Also, you will see some private school players run up some bigger numbers, for much the same reason. There is a lot of talent on those private school teams, but they just aren't as deep, and some of their opponents have trouble just finding enough players to fill all the positions.
You can't compare apples to apples from one district to another, even one team to another. Best you can do is, some teams have web sites that post box scores. Look only at how a hitter fares when he faces the top pitchers.
Our team's top hitter hit .469 for the season, but also was .429 against the top 3 opposing pitchers (all on their way to top D-I programs), including several extra base hits. That tells me he can hit anybody.