I have two objections when people say "school was good enough for me, so it's good enough for my kids."
Firstly, I fear that what we really mean is "school was bad enough for me, so it's bad enough for my kids." Often it is hard to look back upon the way we were parented or the way we were taught and admit that we were perhaps provided with a learning environment that was less than ideal. We are apt to romanticize the past in an effort to justify what our parents or teachers did to us, so that we can rationalize perpetuating the past through our own teaching or parenting.
Which leads me to my second objection: even if our parents or teachers did an exemplary job educating us, wouldn't we still want to improve on their successes?
Think about it this way: As good of a parent you might be today, wouldn't you want your son or daughter to grow up and do an even better job than you did?
If not, what's the alternative?