[TightyRighty]

Well, there is the scene during Snapes memory when Phineas says mudblood (speaking of hearing Hermione) and there is a sharp "Don't use that word." Whether it came from Snape or Dumbledore's portrait - it didn't say but if it came from Snape then you could definitely see his new tune there.

I remember Dumbledore asked Snape if he would promise to keep the students safe and yet he was allowing the Cruciatus Curse to be used as punishment.

[Politicalmom]

I don’t think Snape had much choice, and the students WERE safe, just like Harry was “safe” with the Dursleys.

Dumbledore didn’t stop Umbridge using her horrible quill, and he HAD to have known about it at some point.