Final answer:
The term for when a group believes they have uniquely invented a concept that is actually widely shared is 'conformity to a group norm' or 'groupthink,' occurring when critical thinking is overshadowed by group pressures to conform.
Step-by-step explanation:
The classroom term used for a situation where a group believes that they are the inventor of a concept that was actually shared by many is known as conformity to a group norm or groupthink. This phenomenon occurs when individuals conform to group pressures, leading to a consensus decision without critical evaluation of alternative viewpoints. The intellectual history, as in the 'Hundred Schools' of thought in ancient China, shows us that thinkers often shared knowledge and debated on a variety of subjects, frequently adopting each other's ideas. In educational settings, this can foster a sense of ownership over concepts that are, in fact, widely recognized and utilized. It's a form of institutionalization where a concept or norm is established in society and then taken for granted by its members as an original or exclusive idea.