The magazine goes to all 80,000 K-8 schools in the country. That's inclusive, so it includes K-4 and 4-8 and 6-12, etc. So yes, our magazine does go to K-12 schools. Not sure what you mean by "participating".
I think you'll find that most of our content is geared to a K-8 crowd, although there's certainly a good bit of cross-over between what works for K-8 and what works for older schools.