Griswold High School (Connecticut)  Griswold High School is the only public education institute in Griswold, Connecticut. Surrounding towns (Lisbon, Canterbury, Sprague and Voluntown) have the opportunity to send their students that attended their secondary schools to Griswold. These towns may also send their students to Norwich Free Academy, Ella T. Grasso Southeastern Technical High School, H. H. Ellis Technical High School, Norwich Technical High School, and Marine Science Magnet High School.