In Junior High School! How do I know? Because I have his Report card to prove it!
Dad was always a good student and this report card proves that. I was a little surprised, though, to see two B+s - I'd always thought he'd gotten straight A's all through school. I wonder what instrument he played in the orchestra - I'm guessing it was piano because the only other instrument I remember him playing as a kid was the accordian. He took piano, and later organ, lessons until just a few years before his death. We loved listening to him play as kids and I always admired his dedication to practicing and lessons.
It's interesting that it looks like he moved on to 9th grade in February, 1941 - didn't kids graduate to the next grade in September?