My son or daughter had some subjects waived in high school -- why aren't they automatically waived in college?

There are no "automatic" waivers in higher education. In fact, there are no waivers at all. Rather, under certain circumstances, students may be granted substitutions for some courses. But substitutions will be considered only when the student demonstrates that they are both OTHERWISE QUALIFIED, and that the substitution removes a disability-related barrier to the their academic program.

Remember that ADA provides for reasonable accommodations for students with disabilities. Under ADA, however, it is not reasonable to lower the academic standard. Therefore, requests for substitutions must be accompanied by convincing documentation supporting the claim.

For example, a student with a specific learning disability affecting their ability to learn math processes is majoring in English literature. They have good documentation of their learning disability that strongly supports their claim that the resulting functional limitations may prevent them from succeeding in a college math course. Perhaps they already tried a lower level math course and have been unsuccessful even with reasonable accommodations and tutoring. This student may petition the graduation committee for a course substitution for the math requirement in their general education area. The committee would decide, based on the verification of functional limitations (typically provided by DSS), the substitution options requested, and the impact on the student's course of study. The committee must determine that the substitution would not reduce the academic standard and that it would be a reasonable accommodation for an otherwise qualified student with a disability.

Now consider the same student with a learning disability affecting math, but who plans a degree course in physics or chemistry. These disciplines will have additional degree requirements in mathematics. A course substitution for general education requirements in math will not prepare the student for what is to come in these fields of study. Certainly, they will have a much more difficult time negotiating such a degree program. In fact, their major department would have the right to deny math substitutions, as they could be considered unqualified for such a degree on this basis.