Final answer:
The theoretical school focusing on how international relations are contextualized within broader social relations and how actors define their interests and relationships is constructivism.
Step-by-step explanation:
The theoretical school in question that places international relations in the context of broader social relations and inquires how actors define their national interests, threats, and relationships is constructivism. Constructivism emphasizes that the structures of international politics are determined by ideas, beliefs, and shared understandings among states. According to constructivist theory, these social constructs shape how states perceive their interests, threats to these interests, and relations with other actors in the international arena. This perspective challenges the more traditional views, such as realism and liberalism, by focusing on the influence of ideational factors rather than material forces alone. Constructivists argue that states' interests are not given, but are constructed through social interaction, discourse, and the influence of prevailing norms and values.