Similiar story here, I was told I wouldn't be fit to sweep the streets, I hated school and hardly ever bothered to try, even though I was quite bright, I just never bothered.
Maybe 10 yr after leaving school I employed a lad (had my own firm not long after leaving school), turns out it was the son of the teacher told me I would never do any good, I was sure to remind him when I saw him.
The only class I enjoyed was agriculture, and that teacher ended up working for me as well.