Complex sentence: A second school, initially an Indian school known as the St. Regis Academy, operated for young boys from 1823 to 1829; the school also included a Jesuit seminary known as St. Stanislaus Seminary, which continued to operate until 1971.
Split into simpler sentences: A second school, initially an Indian school known as the St. Regis Academy, was operated for young boys from 1823 to 1829. The complex included a Jesuit seminary known as St. Stanislaus Seminary, which continued to operate until 1971.