Generally reaching out directly to a principal is not the way to go. They have a lot to deal with day to day so if they’re receiving resumes randomly with no job posting they’ll just disregard it. The best bet is to check schoolspring or the employment opportunities section of a specific district’s website. If there’s a opening posted there it will inform you who is the point person to send it to or how to apply.

This is how to get your resume sent to the bottom of a pile in my district.