Through this experience, I have had the misfortune of witnessing students withdraw from the program, not due to their lack of capabilities or knowledge about medical science, but because they could not cope with learning the language that was required for them to be a success on the scheme.
(does the part in red complement the sentence in general??)
I'm not sure of what "on the scheme" means. In AMe, a scheme is usually thought of as being negative. Beyond that, the sentence is fine.