Please answer the following question: Extract the answer to the question from the following context. Question: What were the three schools involved in the debate at the beginning of the 20th century? Context: Between 1892, when Harvard and Yale met in one of the first intercollegiate debates, and 1909, the year of the first Triangular Debate of Harvard, Yale, and Princeton, the rhetoric, symbolism, and metaphors used in athletics were used to frame these early debates. Debates were covered on front pages of college newspapers and emphasized in yearbooks, and team members even received the equivalent of athletic letters for their jackets. There even were rallies sending off the debating teams to matches. Yet, the debates never attained the broad appeal that athletics enjoyed. One reason may be that debates do not have a clear winner, as is the case in sports, and that scoring is subjective. In addition, with late 19th-century concerns about the impact of modern life on the human body, athletics offered hope that neither the individual nor the society was coming apart.
Answer:
Harvard, Yale, and Princeton