Different ones out there for sure. I have a handful of different skis depending on each person's ability.
I have a HO Burner which is a wide body ski that is a little more stable getting people up for deep water starts. It's also pretty stable once up. Finally, for the bigger boys, it has more surface area and will also help them get out of the water easier.
Next, for my 13 and 16 year old daughter, we have a Radar Lyric which is a pretty short, light and thinner ski. This one has more stability for them compared to a single ski from a "match pair" of skis. The matched pair of skis are basically for people just starting out on two and dropping one after being up.
The 16 year old just tried Mom's HO Triumph and did like it. She said it turns easier and quicker. I think both will be migrating over to this one eventually but it's currently a little long for both of them. Still though, they are turning better so that's good.
These are just examples as mine are a few years older than all of the above....but they serve their purpose for various ages.
Another thing you might consider is a Barefoot Boom Bar. Great for learning and teaching kids to ski....and also move up from 2 skis to 1 ski.