Green was also an advocate of close cooperation between public libraries and schools. He firmly believed that students learned best when they had free access to a wide variety of materials and viewpoints. At the university level, Green encouraged librarians to make available volumes which would be of use to students in their classes and to set aside time for the purpose of reference instruction, in order to assist students in independent research. Outside of the university, the relationship between schools and libraries was no less important. Here, again, Green emphasized cooperation between teachers and librarians, suggesting that libraries choose proper books to supplement the curricula of local elementary and high schools. According to one scholar, "the school and the library are practically one enterprise…they interlock…each is imperfect and insufficient without the other."