Your assistant principal is your front line of support.
Unless you’re at a really small school, the teachers rarely interact with the principal. Principals are like the CEOs of the school: they spend more time with the board than the workers. In management, your point of contact tends to be the assistant principal.
And there are many kinds of teachers. Some like autonomy and only need AP interaction during PLCs and evaluations. Others are in the AP’s office every day for a variety of reasons. Here is what you should be able to expect from any good assistant principal. Of course if you have a bad one, none of these are applicable.
A sympathetic ear
Unless you’ve really screwed up, the approach your AP should always take in communications is one of understanding. Teaching is one of the most stressful jobs in the world and sometimes you need to vent to someone who understands. Spouses and friends are great, but you need someone who can relate.
Willingness to give advice
Veteran teachers like to think they’ve seen it all; APs really have. Think about it. They’ve seen every dysfunctional student that has come through your hall, probably multiple times. They get called in on the weirdest classroom stories. This is a wealth of information that they should be willing to share, especially to new teachers who might think their careers are over because a parent is upset with them. Which brings us to our next point…
A buffer between you and the parents
You might try your best, but eventually you will run into an angry parent. They might not even be angry with you in particular. You just happen to be the sounding board. Eventually those angry parents will ask to speak to the AP. When you transfer them, you would like confidence that your boss will have your back (again, unless you’ve really screwed up). Even if they don’t fully support you in this case, they should at least be able to broker an acceptable compromise.
A passion for improving their area of the school
Most assistant principals are put in charge of a hall or grade level. They should always be willing to do anything to improve the situation of their territory, even if it means a change in the status quo that may put them at odds with the principal. It might be a creative idea to remediate a particularly disruptive student. Also, if their teachers have realistic ideas about the hall, the AP should be willing to help implement those ideas. Nothing can improve the lives of the teachers and students in the hall more than everyone, including the AP, working together to make things better.