MPA stands for Music Performance Assessments. These are sanctioned outlets for quality feedback on a variety of musical formats. Each FVA district manages two MPA events per year: Solo and Ensemble MPA and Choral MPA (some larger districts may split these up further for scheduling reasons).
Directors are responsible for knowing and interpreting FVA regulations to their students. Directors are encouraged to study section IV (Annual District MPAs) of the FVA handbook very carefully.
For dates and locations in your area, see your district web site or contact your district chairman.