原句：Because of their children's bad grades, some parents want the teacher Mrs. Müller gone. They meet with Mrs. Müller and try to convince her to leave the class.
修改后的句子：The parents, who are worried about their children's poor grades, want the teacher Mrs. Müller to leave the classroom. They meet with Mrs. Müller and try to persuade her to do so.
解释如下：
1. 将“Some parents”改为“The parents”，使句子更简洁。
2. 将“because of their children's bad grades”改为“who are worried about their children's poor grades”，使句子更流畅。
3. 将“try to convince her to leave the class”改为“try to persuade her to do so”，使句子更自然。
4. 添加逗号和标点符号，使句子结构更加清晰。
