I'd rather not generalize by Division because there are exceptions. just as there are cases at D2 & D3 schools where kids run ~35 minutes for 5miles....
there exist some D1 schools where a back of the pack kid or two runs maybe ~31 minute for 5miles.
low 18s by end of high school is about the bare minimum to be able to simply get on a roster and be taken in at college for an NCAA school. when i say low 18s bare minimum, i mean for a college team that has a PROGRAM and isn't intramurals - in most cases a good D3 school that's large and has organized practices each day.
if you are in this low 18s category, sub 30 minutes 8k probably a good goal to have for your 1st college late august low-key time trial.
of course there are always a few rare NCAA d2,&d3 guys running 35 minutes for 5miles we could cite here, these may be intramural 3-on-3 bball type kids at a primitive ncaa XC program in its 1st year with 5 men on the roster total, we could look them up to prove my point, but lets not make fun.
please correct me if im wrong. this is just what ive observed. i was in that low 18 category