Or maybe it was just worksheets in class, or even a full assessment of knowledge? Because olympiads are usually more serious assignments, often with some kind of selection process, rather than just handed out during a lesson.
If you're talking about everyday school worksheets with questions, it could have been a regular **test** or just a **written quiz**. But if you actually remember a Soviet word for it and it was somehow more formal than a regular knowledge check, it might be an **olympiad** - that word does have Greek roots, but in the USSR it was actively used for written competitions.
There's also the option of **quiz** itself, just with that name. In Soviet times quizzes really were handed out on paper; it was a form of entertaining knowledge assessment. What exactly was the level of seriousness - just entertainment during a break or a full-fledged competition?