[Fomite]

Have you tried to do so? I've seen coherent, well-written letters from a large number of students influence the direction a course took (it was redesigned from the ground up for the next year), and both student and peer evaluations of teaching are definitely a factor in tenure decisions - and depending on the position, may be a major factor.

But I'd start with laying out concrete things, rather than "embarrassed and ashamed".