How do I tell a group to 1) sit down? and 2) stand up?
How do I tell a group to 1) sit down and 2) stand up?
Those are flashcards here on this site. Classroom commands, I think it is exactly what you are looking for.
You use the formal or informal, plural command form of sentarse or levantarse (quedarse de pie or ponerse de pie).
You also have to choose between using vosotros ( sentaos) [Spain] or ustedes-3rd, person, plural for Latin America.)