Chicago Trib article on Notre Dame's InterHall Football. I don't think Sid played, he was training too much for the Bengal Bouts probably! http://www.chicagotribune.com/sports/college/ct-notre-dame-interhall-football-spt-1115-20151114-story.html
Actually, I did play interhall football my freshman and sophomore years. I was a decent HS running back and safety. There were many former HS players on the interhall teams who were much better than I. Some had been all-state. It was very competitive. As I recollect in my increasingly feeble memory, it was on a level equal to HS. My son did not suit up for the games as a freshman walk-on, so he played on his interhall team, which won the championship 7-0, played in the stadium. He threw the winning TD pass from his RB position. We were there. It was pretty exciting. P.S. Back in my day, we wore hand-me-down equipment from the "real" football program, including the old cross-striped helmets. which were used until the early-mid 50s. When my son played, the program had the money from the school to purchase its own equipment.
I played my soph year. I was playing on the freshman tennis team my first year. It was quite an experience for me since my HS in NYC did not have a football team and playing tackle on asphalt was not something for sane folks. We played in the hand me down equipment also. Some of the players were really good. As I recall a great fullback for ND during there '66 NC year was Larry Conjar who was originally spotted playing interhall. There were guys who were all-state in states like Montana that didn't get scholarships but wanted to go to ND. Fun times.