Since this is a high school game, you use NFHS, not OBR.
NFHS Rule 9-7 spells this all out.
True, you cannot both win the game and get a save. I guess I assumed from his question that this was not the issue.
You must go 4 as a starter to get the W in high school ball. If the starter didn't qualify and this was a 7 inning game, then the pitcher between the starter and the closer would get the W. If it was less than a 7 inning game, then the closer in this situation might well get the W, therefore not qualifying for a save as well.
Generally you have to do one of the following:
Pitch effectively the last three innings;
Pitch the last inning with a lead of not more than 3 runs when you entered; or
Pitch less than one inning to close the game, with the tying run either on base, at bat or on deck.
Since the last two don't apply, that's why you have to judge whether he pitched effectively before you can award a save. Sounds like he did, though.