Go back to directory. Add to Address Book. Mr. Mark Leitheiser English Teacher Jr./Sr. High School – Winthrop, MN Work 302 N. Cottonwood St. PO Box 1001 Sibley Winthrop MN 55396 USAwork Work Phone: (507) 207-2298work Email: mark.leitheiser@gfwschools.orgINTERNET Categories: Junior/Senior High School Updated 3 weeks ago. Share on