Thanks for pointing out the ambiguity in my original post. I definitely didn't mean to sound like the student isn't taking it at all! The student is actually thinking that she has to take it before the summer after her junior year in order to avoid a gap year and to go directly to medical school out of college. If she does that, she will be at a disadvantage because she will be taking classes in the fall, winter, and spring. (Taking the MCAT while taking classes can be very busy.) By "top student" I mean that everything she's done so far has been top notch. She has a lot of potential and I don't want to see it blown by a scheduling mistake. That's her situation.
If she were to apply on June 1st after her junior year and take the MCAT in August after her junior year, would that put her at a disadvantage? How so and how much of a disadvantage?
OK, I feel badly for commenting so harshly on a complete misinterpretation of your original post (and for throwing my 2¢ in on the epic tangent which is brewing) so, while I'm hardly an expert, I'll try to answer the actual question at hand.
Here's the deal: whenever discussing any less-than-ideal application decision, nobody is ever going to be able to definitively state 'how' bad something is or who could absolutely get away with it. It's just not possible to predict exactly how things will shake out. What we
can do is to go over the timeline and talk about why the ideal is ideal and how much each other possibility deviates from that ideal. At that point, it's the applicant's judgement call as to whether the disadvantages of that course of action outweigh the perceived benefits.
So here goes:
AMCAS opens for submission on June 3.
Once you submit, it takes an unspecified period of time (which typically gets longer the more you wait) for them to sort through and 'verify' your transcripts. No school sees the app until after verification.
NO school sees ANY app until the end of June (somewhere around the 27th), even if it was verified on June 04.
You can submit and verify an app without an MCAT score, but schools won't look at it until it is complete.
So, the ideal is to have the MCAT score in and to have your app verified by the end of June.
The next best scenario, given the often-lengthy verification process, is to submit the app in June with a pending MCAT. You can submit to only the schools you
know you want to apply to, regardless of score, and then add in others once the score comes in, based on what you get. At this stage, the date of your MCAT score report essentially determines when your app will first be seen by schools.
Sooner is still better.
If you have a solid app other than the unknown MCAT result, and end up scoring well, you may not be hurt much if schools see you a month or so late - which would be a late June/early Aug test date. However, even a great applicant will be poorly served by waiting until September or early November (which is when schools would see an August MCAT). At that point, most schools will have had several rounds of interviews and some will have started sending out acceptances - aka fewer seats are available. If that MCAT turns out to be lower than she would hope? Bad news bears.
So, it's doable, but nobody will tell you it's ideal, and nobody can say 'oh, but for a 4.0 student it will be fine.' A 4.0 student will fare better in that situation than a 3.4 student, but it's still a disadvantage. Either way, a lot rides on that one, un-retakeable MCAT score.