Little Ernest
Ironically enough, I was talking about this movie with a co-worker recently when one of my managers passed by. He asked if we were talking about "Ernest Scared Stupid." When we confirmed that we were, he admitted to having played little Ernest in the scene with Ernest's teacher.
His age (26) and facts about the movie check out. Plus, this is a rather vague and low-budget movie to brag about having played a D-role in, so I am in full belief that it was him in the movie.
I found it amazing that I now work with someone from that movie, given that it holds such a special place in my heart.