Higher standards can help students who have no impediment, but is simply another roadblock for those who can't perform. The analogy I use is the student with one leg. Suppose a teacher required all students to run the hundred in under 15 seconds. I don't think anyone would say it would be fair to expect the same from the student with one leg. However, we raise the standards for mainstreamed students with learning disabilities and so often, since we can't see a physical aliment, we decide they just need to work harder.
Higher standards are good for everyone.