I don't know of any rink that allows 5-person semi-privates for the very reason that it's a small group. Most rinks cap semi-privates at three students. The group size and ice needs are too much for a public or freestyle session. Plus, it cuts into the group lesson program enrollment, which produces more money for the rink than privates.
I teach groups as one lesson. No one gets "individual" attention for more than a minute or two at a time. I usually arrange the students so that I can instruct each of them on their style, but I speak to, and demonstrate for, the entire group in between each attempt.
The problem is in mixed-level groups: you have to plan your lesson in advance so that you can have two Basic 3 skaters doing two-foot turns on the circle while the three Basic 4 skaters are working on one-foot turns using the heart-top tracings I draw with my marker.
Last year, our schedule had two different group lessons scheduled back-to-back. The first half hour, I taught one (1!) skater at the FS1 level. The second half-hour, I taught three FS1, 2 FS2 and a FS3 skater. The rink was paying me the same amount for both sessions, so I asked all the second-session FS1 parents to come for the first lesson instead, so that their skaters would get a more focused lesson. It also made the second lesson easier. Win-win all around.
When I substitute, I can't always find common elements, so I split the class physically and skills-wise. That means they have to practice on their own a bit, but I check in with them from the corner of my eye, even if I'm working with someone else, I'll call out "() - you're dropping the free hip. Hold it in check."
That's the ideal, but not every group lesson instructor can manage that, so they turn a group lesson into a series of private/semi-private lessons. I've heard instructors say "Well, there are three skaters, so I give each one ten minutes." I'm not a clock-watcher, (and I never wear my glasses, lol) so I wouldn't feel comfortable rationing the time like that, I'd be afraid of a student feeling cheated. (Perception is interesting: the students who've complained about other instructors are usually the ones who have the "first lesson" in this situation. They may be getting their allotted time, but being left on their own for the remaining 20 minutes tints their perspective.)
I will say that, if the issue is that a handful of students need assistance to skate, the instructor should be able to ask the Director to assign a helper or recommend a few ramp-up private lessons. If the one-on-one imbalance persists for more than two or three lessons, that's definitely an issue. I don't know how to broach the subject between a student and the Instructor or Director - you'd have to be very diplomatic, so as to not complain about the instructor, but get the assistance needed to make the class a success. At many rinks, the Adult instructors stay the same throughout the year.
I've had students in NY change days to avoid a particular instructor that they didn't like or that they preferred - maybe that would work in this situation so you could avoid the student who monopolizes the class.
In a lot of cases, the skaters don't practice at all, which makes every lesson a supervised practice and review of the prior week's lesson. While they may think it's too hard to pass the levels, the reality is that they're holding themselves back by not practicing and coming prepared for class each week.