It may help to tell what specifically the company noticed as a problem. There are a ton of drivers your age out here. Every CDL driver passes a DOT Medical Exam and some trucking companies have their own strength & Agility tests. Thoses tests, except for flat bed, are usually pretty tame things. The companies that recruit at your school are not the only places to work. Usually they are the mega companies needing as many drivers as they can get. They aren’t often the very best places to work. The strongest recommendation I have about trucking is FIRST, before ANYTHING else, find a company you want to work for. You don’t want to borrow money for CDL school and not be able to work afterwards.
I suggest you get an account on TheTruckersReport.com and post your problem in the New Drivers Section. There are many companies that will hire you.