At the moment, there's no way to turn off "new class" notifications for teachers: whenever a teacher is added to the Roster for a class, they'll receive a notification (provided that they have a confirmed e-mail address). If this is something you'd like us to consider for a future update to our notifications tools, I'd recommend posting to our
Haiku UserVoice Feedback Forum. There's an existing idea about
domain-level controls for notifications, but if that's not quite what you're looking for, feel free to start a new thread!
Note that students and parents will only get a notification if they have confirmed e-mail addresses and are manually added to a class that's already Active. As a result, they'll generally receive fewer "new class" notifications than teachers.