Could my principal provide a letter of recommendation or does it have to be from my subject teachers for a Master's?

Yes, your principal can provide a letter of recommendation, but U.S. master's program admissions committees usually prefer letters from subject teachers or professors who know your academic work directly.

A principal's letter may highlight your leadership or character, but recommendations from teachers who have taught you in relevant subjects typically carry more weight because they can speak to your academic abilities and readiness for graduate study.

If possible, prioritize recommendations from subject teachers who are familiar with your academic performance.