But personally... I think you are making a massive mistake.
Not only are you allowing/encouraging your children to sell themselves short which can only end in a life of regrets. But you are hurting society in general too, by depriving it of honest productive citizens which are in desperate short supply.
And on top of all that... there is the issue of marriage. College is where you want your children to find their mate. There is a short window of opportunity to find a quality mate after high school before they are all taken and you are left with nothing but players, people with massive psychological baggage or issues that will affect their lives forever like marrying someone divorced or with kids from someone else.
Well, I can only speak from personal experience, but my only regrets are that I spent too much time on BS and not enough on life when I was younger--and this comes from a person that spent very little time on BS! My view is that people who are going to succeed in life are people who are going to succeed in life.
As a note on marriage, I think a lot of divorce depends on the circles in which you run. We're (my wife and I) thirty-somethings, and in our circle, we don't know anyone who is divorced. Divorces are disproportionately skewed towards the lower class. Keep out of it and you're much, much less likely to divorce. For my own marriage story, I met my wife while I was in graduate school. I attended a good graduate school, but I got in by virtue of very good test scores. I wasn't particularly interested in college, and my grades reflected that lack of interest. If I applied myself in college, maybe I would have attended a better graduate school--but then I wouldn't have met my wife or had my daugher.
Scary to think of the road not traveled.