Complex sentence: The School continued to pursue archaeological research projects on a modest scale and was headed, successively, by Sylvanus Morley, Boaz Long, Wayne L. Mauzy, Edward Weyer, Jr., and Eugene McCluney.
Split into simpler sentences: The School continued to pursue archaeological research projects on a modest scale. It was headed, successively, by Sylvanus Morley, Boaz Long, Wayne L. Mauzy, Edward Weyer, Jr., and Eugene McCluney.