Looks great! You just need to make one correction. You wrote the following: A few weeks before, these students had expresses disagreement...' It should say: A few weeks before, these students had expressed disagreement... (express needs to be in the past tense). I hope this answer helps you. If you are interested in taking English lessons, I am a professional English teacher, and I am currently accepting new students.

Here are my suggestions. The school's principal finally bowed to pressure. He agreed to satisfy popular demand allowing the students who hadn't obeyed school rules to return to class. A few weeks earlier, these students had expressed their disagreement with the school's decision forbidding the use of smartphones in school. Hope it helps.