Google News Archives provides a historical record of news dealing with UNESCO from its files. Note that the frequency of news stories was high in its early years, decreased during the late 1950s and 1960s (the period of decolonization in which many new nations joined the Organization. There was an increase in news related to UNESCO in the late 1970s, when the New International Information Order debate was hot in the United Nations, and in the mid 1980s, about the time that the United States and the United Kingdom withdrew from the organization. The archive contains fairly large numbers of news stories in recent years.
If you go to this site, you can actually view stories from the archives, learning about UNESCO's history for yourself.