I am at one of at least two institutions which would like TA's to be able to grade student work without having access to view the entire gradebook.
My ideal solution would be to give TA's "write" permissions to the right hand side of the SpeedGrader, but not "read" permission. Access to a single assignment group would also solve my problem (for instance, a TA could see homework grades but not exam grades).
Workarounds such as offline grading and peer review do not scale well. We don't have the staff to train and support new TA's each year for a clunky workaround.
A similar suggestion was made by anna_oh about a year ago. We have contacted our CSM, who referred us to this forum.