I have to disagree with the older answers from Buzz and Brian Borchers.
Access to teaching evaluations is a matter of individual university policy.
At my (flagship public American) university, teaching evaluations are (by default) strictly confidential to the person being evaluated; whether that person is an instructor or a teaching assistant makes no difference. There are only three exceptions to this default, all of which formally require the permission of the person X being evaluated:
- X can give permission to be considered for a teaching commendation.
- X can give permission to share their evaluations with their department chair/head.
- X can agree to a request for a summary report from the department, as part of an application for tenure/promotion or an award.
For all three of these options, only a summary of numerical scores is actually shared; narrative comments are not.
In particular, I have no official access to the teaching evaluations of either the teaching assistants for the classes I teach or my graduate advisees who are funded by TAships. Even the faculty and staff who assign TAships cannot see the previous student evaluations of prospective TAs.
(Of course, in principle, anyone can share their teaching evaluations with anyone else, but in practice, because the campus treats the evaluations confidentially, nobody does.)
I don't think this is good policy, but it is long-established and well-defended policy on my campus.
On the other hand, at my undergraduate institution, teaching evaluations of all faculty were effectively public, including narrative comments. There was a large printed book on the desk at the registrar's office that contained complete evaluations of every class from the previous semester, with numerical scores summarized and narrative comments transcribed (and presumably edited to remove personal information) from the paper evaluation forms. Every semester, the student newspaper would publish a list on the front page of the ten highest-rated and ten lowest-rated classes from the previous semester.
Apropos to this question: Teaching assistants did not get individual student evaluations; they were evaluated only indirectly through their effect on their class.