I'm a chess teacher/coach for a couple of children (age 14-18) at my local (not very big) chess club (we're all member of this club). Due to various constraints on my and their part, all the time I get to see them regularly is a single session of 30 minutes per week. (I do watch and comment on their games or jointly analyze them once in a while, but this isn't exactly regular)
Some background on my current teaching methods
I'm teaching them 'Stap 4' (step 4) using the 'Stappenmethode' (step method) by Rob Brunia and Cor van Wijgerden, de-facto the teaching method in the Netherlands for quite some time.
For people unfamiliar with the method, 'Stap 4' corresponds to advanced tactics (Double attacks on fields that are again some double attack, advanced 'luring', particular sacrifice mates, etc.) and introductory strategy (a bit of intermediate end-games, pawn structure and attacking the king). The method provides lesson outlines and other advice for the teacher and a book with diagram problems (puzzles) for the students to practice the material from the lessons. The problems are 5 ply deep on average. Every 'step' can be concluded by a written exam and a diploma that consists of solving a set of diagram problems under a time-limit (as usual for exams). (The diplomas aren't a requirement for anything, but they're nice for the kids to have)
...and on my teaching skills
I think I'm decent at teaching small groups of (sufficiently) motivated students, which my students are. Most of my teaching experience (in addition to teaching chess for about 5 years at my chess club) is from being a student assistant helping in tutorial sessions at my university and tutoring fellow students in high-school.
I think I'm decent at explaining things related to topics at which I have expertise (perhaps my activity on Computer Science can convince you of this) I'm not very good at maintaining 'order in the classroom' and related educational skills, but these are fortunately almost never needed with my current group of students.
I'd like to think I'm a honest (perhaps too honest at times) and enthousiatic teacher, but I also think that I'm the least qualified person to judge me! (unfortunately, I'm the only person on this site who can judge me, so it'll have to do)
All in all, I don't think my teaching skills are a problem, but do let me know if you disagree.
The kids I'm teaching aren't chess geniuses, but I think most of them are bright enough to pass the exam, given they're properly prepared. I'm not a chess genius either, but capable enough to teach them. (My actual ELO is pretty low as I mostly play at the club instead of rated tournaments, but you may put me around ~1900 ELO with decent knowledge of strategical elements)
My problem is that 30 minutes is pretty short, in fact a lot shorter than the authors of the method advice. In particular, the authors stress the importance in the teacher's manual of letting the students practice 'special games' related to the lesson's topic (e.g. endgames starting at a certain position) against each-other. I simply don't have the time to do this. (I do manage to squeeze in a simultaneous game of an endgame or such of them versus me once in a while)
Most of the time is spent with me explaining the material of the lesson, covering about half the examples provided in the teacher's manual and commenting on the (incorrectly solved) problems they handed in as homework. Sometimes, I put the method aside for a lesson to discuss their recent games instead.
What I tried
I've stressed to my students that the limited time means that they should take their homework very seriously (which most appear to do), but I'm still worried they fail the exam due to insufficient preparation.
I've tried to offer additional online practice using lichess (the 'study' feature in particular), but this has turned out to be too time intensive for me. I've considered letting them play each-other online, but the difficulties this gives me for me to comment and 'control' their match (such as halting their play, letting them take back moves or look at variations, or just talking to them) made me think this wouldn't work.
So, what additional material/practice for outside the class or more effective teaching methods for our limited time in class can you suggest to me?