No there isn't a way to opt it for which there are valid reasons.
Reasoning being is by giving everyone a computer they can ensure all software downloaded with it complies with the required testing/education software and they have a way to regulate the software on your computer. You might say to yourself "that's dumb, i could just download this on my computer, but theres all kinds of crap that affects it. As an example, New MacOS software updates aren't immediately compatible with certain software so they will automatically update on everyones computer after a reviewal process.
In addition when we had to access NBME exams which required us to sign into different computer profiles which I don't know how would be done if the administration didn't have remote access to install the proper software/drivers or whatever.
In the past students did bring whatever laptop they had but it constantly caused problems with using the required software. Forcing everyone to buy a computer is an easy way around this. Fortunately, mac's retain their price relatively well so you can always sell upon graduating.
I sold my old 1 and just use the new mac. Other students use the new mac exclusively for testing and retain their old computer for everything else. All up to you.