It's a rear exit exhaust.
I would be REAL careful buying any motor that was used for shop class. A few years ago I got my hands on about five brand new Briggs 3HP engines from a local high school. The kids tore them down and reassembled them, and man oh man what a mess. Backward pistons, carbs clocked wrong, upside down/busted/missing rings, case bolts in the connecting rods, etc. I was hoping to make at least one good engine out of the five, and they were all so messed up that it wasn't possible.
And none of them were ever fired, so technically they are "NOS"....