St. Mary School is fully accredited by the Wisconsin Religious and Independent Schools Association (WRISA). WRISA is a state chapter of the National Federation of Nonpublic School State Accrediting Associations, which is recognized by the College Board and the Office of Non-Public Education, an office within the U.S. Department of Education.

WRISA's three-phase accreditation process provides school communities with the opportunity to explore every aspect of their school program through a self-study, receive valuable feedback from a team of impartial professional educators, and develop a long-range plan using the WRISA framework. Once accredited, schools file an annual report documenting that they are in compliance with the WRISA Standards and that they have made progress on their long-range plan.