Believe it or not, some students mistake a possessive apostrophe (students’ confusion) for a comma (students, confusion). Oh, my, let’s set the record straight.
You have students who possess something. Therefore, you use a possessive apostrophe like this:
One student has something: Let’s overcome the student’s confusion in completing a task.
Two or more students have something: The two students’ confusion was palatable.
Neither of those examples needed a comma. Anywhere.
Do not use a comma between a subject and a verb. For example, I saw something like this today:
The students, confusion was palatable.
No, it wasn’t. (Well, perhaps it was but this is not the way to write it.)
The groups, formation…. Nope, that doesn’t cut it, either. Instead try the following:
The group’s formation was spurred on by Jim. (Actually, this is passive voice construction. To make it active voice, write it as follows: Jim spurred on the group’s formation.)
Hope this helps!