coolcoach is right. if you are on a coed team, you more than likely will be doing both. depending on the school though as a incoming freshman you might be middle layer, just for experience reasons.
Are they taller than the top girl and is it possible for a female base in high school to make the transition to a middle layer girl in a coed collegiate squad? Thanks!

as far as height is concerned it doesn't matter if the middle layer is taller or shorter than the top girl, just as long as the two middle girls are about the same heights, so that the top girl can stand on them evenly. a lot of middle layers know how to base as well, this helps them, because its just like basing, but in the air. as long as you can do a toss shoulder stand and are able to stay extremely tight, then of course a you could be a middle layer in college.