1. You can access basically all answers given via the Expression Manager and also insert it this way into the email templates. Please refer to the manual about Expression Manager, because how to address the answers depends on the question type. There should also be quite a few answers regarding on how to send "reports" via email or how to create reports at the end of the survey here in the forum.
2. As far as I know, you can use equations in this email field, so you can insert some equation there. However, I would probably process this in an equation type question before, in order to not fill this field too much. In the equation you could could create something like:
Code:
{if(math>50, 'teacher2@school.com','')}
Code not tested, just an example on how to think about it. You need of cours include the ifs for the other conditions. Then you just call the result of this equation type question into the field for the email addresses. Should work, but will require some testing.