1. She did her part, and the native speaker did her part. They were cooperative and did their parts properly.

2. Teachers should make students say, act out and work together in class.

3. The quality of a teacher's voice is important in teaching. If she shouts loudly to stop students' making noises, she may hurt her voice. In co-teaching both teaches' voices are essential.

4. As the Korean teacher explained what the native speaker said, students have no difficulty in working with the native speaker.

-------------------------------------
I have written down what we can think of after co-teaching. Would you correct the sentences,please?

1. She did her part, and the native speaker did her part. They were cooperative and did their parts properly. This could be written more simply and concisely: She and the native speaker both cooperated and said their parts properly.

2. Teachers should make students say, act out and work together in class.
I'd make a few changes: Teachers should make students speak parts, act out roles, and work together in class.

3. The quality of a teacher's voice is important in teaching. If she shouts loudly to stop students' making noises, she may hurt her voice. In co-teaching both teaches' voices are essential. Sounds good. One suggestion and one correction, though:

"...to stop students from making noise..."

"...both teachers' voices..." (the "r" was left out of "teachers'")


4. As the Korean teacher explained what the native speaker said, students have no difficulty in working with the native speaker. The only problem I see here is verb tense. You have "explained" (past) and "have" (present). You should have both be past or both be present.

Certainly! I can help you correct the sentences. Here are the corrected versions:

1. She did her part, and the native speaker did theirs. They were cooperative and fulfilled their roles properly.

2. Teachers should encourage students to speak, act out, and collaborate in class.

3. The quality of a teacher's voice is important in teaching. If they shout loudly to stop students from making noise, they might strain their voice. In co-teaching, both teachers' voices are essential.

4. As the Korean teacher explained what the native speaker said, students had no difficulty in working with the native speaker.

I have made some minor changes to improve the clarity and correctness of the sentences.