there are very few sub 920 HS guys who don't go D1. VERY few. 920 will win the state meat in more than half the country...we become accustomed to treating it as average because we routinely see 8:50 guys in the headlines, and forget how tiny of a minority that is...there are a lot of D1 schools with a lot of open spots. if you're going break 920 you're going to get a good amount of scholarship offers (at least partial, probably a few full). not to mention how many 915-945 guys have gone on to be DI all-americans...that is a very, very long list...
as a 926 HS guy who made the choice myself (to go D1) a few years back, i can say with a humble amount of authority that everyone i closely competed against during HS, wound up going D1 in college, even if it wasn't the best choice, and even if they didn't improve/compete well over all 4 years.
personally, just my view of things, but i'd say the "line", or territory where you have to make the choice, is closer to the 9:55/435 range. maybe it's only me who has seen the enormous improvements guys make in college, but my small D1 school alone had a 432 HS guy who wound up going 4:02/1:51, plus two 9:50ish guys hovered around 30:30 for 10k and mid 14's for 5k, plus, most miraculously, a 4:44 hs miler who ran 8:46/14:50/31:07. i thrashed all 4 in high school and freshman/sophomore years, spent my last two years chasing them, for the most part, once they developed. our 9:19 kid we brought in when i was a senior ran 13:57 as a junior last year. everyone is different - but anyone who shows potential to run under 10 minutes, 435, 205 in HS, and displays the necessary fearless work ethic, could certainly go D1. it's not as elitist as it is made out to be.
the trouble is, you get guys who run 920 in high school and they want to feel like they belong to some sort of exclusive club, when the reality is that the race has just begun, and those 9:40 and 9:50 guys are going to haunt their footsteps.
all that said, D3 offers a lot of great opportunities and some better small academic schools, as well. check out nyu and haverford on the east coast. i wish i'd considered D3 possibilities more carefully.