Nor can the company proprietors in some cases. Ex RAAF working for a school in MB told a student after a flight to give it up as his considered opinion was that the student didn't have what it took. Proprietor went ballistic at the loss of income and instructor departed shortly afterwards.
Or maybe the proprietor went ballistic at the fact that instructor had decided it was his role to "scrub" students rather than train them. Not everyone will be an ace on day one, some of the most learned, mature flyers I know had problems when they were training, substantial problems that required changes of instructors, schools or many repeats until they achieved the required standards. These hurdles give troubled students the extra maturity they need in order to improve. Sure they wouldn't have passed 2FTS, but that's not the environment they're in.
If it's an attitude problem rather than an aptitude one, you might also need to be sat down and told that your attitude stinks, and it needs to improve. It happened to me. Twice. And it worked.