Generally, the sentence final ending "-자" is used when ordering children to do something in school, like "Let's do something" in English.
These rules were very common in a elementary classroom in my school days, except for the 4th sentence.
1. Show respect to all students and the teacher.
- 선생님의 말씀을 잘 듣고, 친구들과는 사이 좋게 지내자.
2. Raise your hand during class.
- 수업 중에는 손을 들고 선생님께 질문하자.
3. Finish all class work.
- 수업 과제는 반드시 끝내자.
4. During class try your best to speak English only.
- 수업 중에는 영어로만 말하자.
5. After class clean everything around you.
- 수업이 끝나면 교실을 깨끗이 청소하고 정돈하자.