Let's see if we can work it out. We may need to consider some further enhancements for getting the desired effect.
The Dataform has a built in tool that creates a blank entry for each user in the course. It's manual so at this point if you want to create an entry per interval you need to run this tool once every interval.
Another possible approach to a similar effect could be by using only one entry per student with all the fields needed for all intervals and using views to break down the entry to separate "intervals". This could work with a reasonable number of intervals and fields.
To restrict teachers' access only to their group's entries I think that we would have to add a capability. I will look into that.