Danea,
You really want to start a new topic with this question.
Meanwhile, students should not still have editing abilities after 30 minutes. If they do, and if it is in all forums in all classrooms, someone has changed a global permission (changed it site wide).
There is a permission to "delete own post (anytime)" in the student role. If that's what you mean by "edit," check the setting. The default setting appears to be "not set."
Forum
Is it possible to change 30 minute limit for Q&A forums?
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