In a Stanford CS project-heavy class, the projects are usually 50% or more of your final grade, and those are pretty tough to do without some understanding of the material. In a problem set class, the exams are typically 50% or more. For example, in CS103 (learning the basics like proofs, induction, graph theory, set theory, a little complexity, etc.) your grade is 45% psets and 55% exams; in 154 (in-depth complexity), it's 40/60. In 248 (3d graphics) it's 90% projects, 10% exam. So even if you get a TA who helps a little too much on psets, you won't get better than a B without understanding the material.
It depends on the college. I would imagine that Stanford would be a bit better quality than my school.