The answer to this question depends largely on the approach the teacher or school chooses to take to world geography.
In its most literal form, a world geography class would cover the countries and cities of the world, including their topographies (the volcanoes, canyons, oceans, seas, rivers, and more which comprise the land and water of each place). This kind of world geography course would probably be considered a physical science class.
Another option for a world geography class is to study the people of each country as well as the countries themselves. This is more likely to be considered a social science class because it would probably include discussions about how the land shaped the people and how the actions (or inactions) of one group of people affects other groups. A course like this would probably include studying the human, political, cultural, social, and economic aspects of each country and its citizens.