More recently another boy I know left the expensive private school he'd been attending because the teacher said he had learning disabilities. He was functioning academically far below grade level, but that might have had something to do with the fact that the teacher blamed him for every problem in class and he was often punished for things he hadn't done. After one year in public school his academic levels were normal and he was a much happier kid.
On the other hand, I had two preschool students whom I suspected had learning disabilities. In one case the parents had the child tested and got him into an early intervention program so he did well in school later. The other parents were in denial about the problem and didn't have the child tested for years, by which time she had learned to think of herself as a failure.
Teachers are not medically trained and are not qualified to make a diagnosis but if a teacher suggests that a child may have a learning disability it can't hurt to have testing done. Better safe than sorry.