Well I think you turned out OK
The father at your son's school is obviously over doing the yelling and hitting. I believe in spanking, but only when it's necessary, when a kid is deliberately being disobedient. I respect my parents and grandparents, even though they spanked me.
I was even spanked in school, something that was accepted in South Africa until I was in like 7th grade. A lot of the times the teacher would give you an option if you wanted to get hit, or if you wanted them to let your parents be notified. I always went with the first option, and so did everyone I know. We were never abused or beaten. I'll tell you that we never had any problems with kids shooting up schools or anything like that.