Taking courses at WGU not part of my degree program? And credit by examination

[sciencemathematics1]

I want to complete a BS in computer science at WGU. However, there are other degree programs in the WGU teachers college which have courses in their curriculum that I would like to be able to take. I want to take math and science courses from the teacher's college program. However, I talked with an enrollment counselor there and they told me that I could not take those courses if I was in the computer science program, because they are not part of my degree program. Is there still any way to be able to take these classes?
There are a number of classes in the math for teachers and science for teacher programs that I would want to be able to take.

I also was told that if I knew the material for a class, then I could go directly to the assessment for the class to get credit for it. Does this apply to all classes at WGU, since they are competency based?