You always apply with the school or district that's hiring. The button on each posting tells you how.
Apply on the district's site
Most postings open the school's own application page. You apply there, using their system and their account if they ask for one.
Apply on EduJobs
Some schools collect applications on EduJobs. Those postings show a short form right on the page, and search results say Apply now. See Apply on EduJobs.
Apply by email
Some postings give an email address instead. Selecting Apply by email opens a new message in your email app.
Note:
If a posting has no application link, check the district's careers page for that role.