SambonInteresting question. I'm not sure there's one definitive word or phrase I looked at, but here are a few things to notice:
First, let's look at the wording of the conclusion itself. Granted, it could be seen as ambiguous, but note that if the author had simply wanted to look at percentage of the total, they'd just be comparing number. In that case, they could simply have said "for-profit colleges enroll MORE disadvantaged students" or "a greater NUMBER of disadvantaged students." The fact that they used that lengthier phrasing is itself evidence.
Second, keep in mind that while arguments in Assumption Family CR (assumption, str/wkn, evaluate) will always be flawed, they should still be somewhat reasonable. The conclusion as I interpreted it is much closer to the premises. Sure, it's theoretically possible for the schools to serve far fewer students overall and still serve a greater number of disadvantaged students. (For instance, maybe ALL or nearly all disadvantaged students go to for-profit schools.) However, this doesn't stem in any reasonable way from the premises. However, as long as we assume that aid received is actually a good measure of aid needed, then the other version of the conclusion actually works pretty well. So the argument has one main flaw (how meaningful is it that more aid is received per student?), rather than a wildly disconnected conclusion. That's how CR typically works.
Third, it's also worth bearing in mind that the premises are also about proportion. We just know that the aid going to these schools is out of proportion: it's more than we'd expect given the number of students enrolled. We don't know anything about how much aid is actually received. For all we know, these schools only receive 1% of total aid. It may just be that we'd EXPECT them to receive even less.