Complex sentence: Olcott Estate is the administrative headquarters of the Theosophical Society in America and the home of the Illinois State Board of Education DuPage County branch which conducts on-site courses, seminars, workshops, and lectures for members and the public.
Split into simpler sentences: Olcott Estate is the administrative headquarters of the Theosophical Society in America. Its education department conducts on-site courses, seminars, workshops, and lectures for members and the public.