He currently plays Tier 1, EHF & Town Hockey.
Top 2-3 on his town team, bottom of the pack on his club team
He will be fine, stay positive and keep doing what your doing. Unless your local high school is a powerhouse even the Tier 1 kids are top contributrs to the team.
Plenty of middle of the pack Tier 1 and AAA kids go on to be the top high school players on their team and area.
And remember to set a realistic goal for yourselves and child, unlike most of the fruitloops on here. If your kid has enough skill to be a captain of his competitive high school, then that is a thing the majority of youth hockey players never reach and means a great deal to them, but if your illusions of grandeur have him playing at a top NCAA school then that high school captaincy seems like a disappointment if that's his pinnacle.
I'm sure a very accurate answer could be given with more info like which EHF Tier 1 team and where he will go to high school.
Either way, he wil be fine and be vastly better than the kids who played just town going into high school, unless he is struggling with his EHF team