That's funny, I've never picked my son up from school in my car out of fear what the teachers might think and say.
I pick my 8 yr old up from his private Christian school all the time. I do get some funny looks from some of the conservative parents but all the kids think its great when I come rumbling through the parking lot to pick him up. You can see the glee and excitement in the kids faces and it makes it all worthwhile.
He rides in a booster seat up front. I only have a harness bar but I don't like it sitting right in front of him when he is in the back seat. A cop pulled up alongside of me one day and suggested I put him in the back. I pointed to the bar and he just said, "Oh" and drove off.