Some schools allow teachers to limit the number of recommendations they write. Often, first come, first served. So it may make sense to ask teachers whether they would be willing to write a recommendation at the very end of junior year or during the second week of school senior year (not the first week, when teachers are overwhelmed with other work, like straightening out kids’ schedules).
Also, some teachers want a resume or brag sheet of some sort so that they can be sure that anything they say about the student’s extracurricular activities is correct.
One of my kids applied to colleges early decision, but the teachers wanted to write all of her recommendations at the same time. So she had to finalize her full list of colleges in time for the teachers to write recommendations before the ED school’s deadline. We were not aware that this could happen, and it was a challenge to come up with a final list that quickly.