Now that we can see our kids' classes first-hand, it is easily apparent which teachers are strong and weak. Some of the weak teachers are also the most unfair and difficult. I feel compelled to speak up about this, to confront the teacher and also send a note to the admin...but not sure whether it could backfire. Any thoughts?

PS-this is a private school
DD attended private K-12 and while I would say that her teachers were good overall, there were some definite disappointments along the way. I would caution you to be very careful when it comes to making teacher complaints. This is for several reasons: 1) It's just life that you (and your DC) will like some teachers more than others; 2) Part of what your child is learning is how to deal with teachers (and others in authority) who they don't like and whose style doesn't match their own--it's an important skill; 3) Practically, you could be labeled a complainer or alienate the teacher and that won't help you or your DC; 4) The administration wants to provide cover for the teachers (private school parents are demanding!), so unless it's a really obvious case of incompetence, you're unlikely to get the response you want.
Ultimately, in the 13 years of DD's schooling, I went to the administration ONCE (when she was senior) about a teacher--and over a very egregious situation. The administration readily agreed with me and took me seriously--in part because they knew I wasn't making a fuss over every injustice or every mediocre teacher. Also, a number of other parents had complained about the teacher, so they knew I wasn't an isolated case. If a situation is *really* bad, you can bet that other parents are complaining. Let them do the dirty work and keep your powder dry for the TRULY important stuff. Believe me, when a situation warrants it, you'll *know* that you need to escalate it and you'll want your credibility in tact.
Thanks, very good advice
My kids are in NYC public. It is very eye opening to listen in on these classes. I agree with the advice by the poster above. Pick and choose your battles.
I agree with the poster above/. Curious though. How are you defining "bad teacher?"
basically a non-teacher. Just introduces a topic, then has kids start doing practice sheets. Reviews homework late or never. Gives test without any prep and with crazy questions.
Send a note. We have had conversations with A couple of teachers this year