I usually do but not this time, wanted to start a discussion to see what other students might think about it. I have come across issues of this kind quite a lot and wondered if maybe there is something wrong with the way I see things. But until further notice I believe that as Swahili has neither definite articles nor indefinite articles, solutions with and without articles should as a rule both be accepted (unless they clearly make no sense). The same holds true for the use or not use of the continuous present.
As far as I can contribute to the discussion: both of the answers you suggested are fairly clearly correct as well. Most of the time, the lack of alternative answers added to this course is the main problem. There's no (or little) harm in reporting something even if you're not sure. It might annoy the creators a bit (with their huge backlog of reports) but they will sort out the ones that aren't correct from the ones that are. If in doubt, report ... and you can report something and have a discussion about it too.
You are more than right. After reporting several issues without anything being solved in a reasonable timeframe, you lose motivation to report. Especially when it comes to these kind of ridiculous bugs. Students has been accepted many times before, suddenly it is not correct anylonger? I know its free, but if the moderators are not taking it more serious I also wouldnt see a reason why we would have to pay for it...
I entered "They are teaching students" on June 17, 2018 and it was marked wrong because I hadn't added "the" in front of students. So it looks like both students and pupils are now accepted. I don't understand though how I would know the sentence talks about students in general or particular students.