Perhaps the best policy is to make a note that these children are gifted, stand by while they do their own thing, and when and only when they start getting bored, give them access to the kinds of challenges they need.
In my case, that would have been great. I had a few teachers along the way who allowed me to shed some of the shackles, and by the end of the year, my grades were always over 100%. Those are the teachers I really admired and felt I learned the most from. In my high school freshman year, by the end of the year I'd done all the work from my Honors Bio 1 class and the Honors Bio 2 class, and had loved every minute of it.