I have taught this senior tap class for the last 2 years now, there are 6 of them and I have gotten them up to quite a high standard. They are aged between 16 and 22.

This year the SO has told me some of the younger students need to move up a level, but due to time table issues they will be joining my senior tap class. They are 13 and 14, good little tappers but they are way behind the girls they will be joining.

I have taught different levels in one class before but only with younger students and using an assistant teacher. How do I teach all these students without the older ones getting bored or held back, or without scaring the younger ones off or getting them left behind?

YIKES, 13-22? She's going to alienate the daylights out of those older girls. Poor girls...

I had to combine my tap 3 and tap 4 this year due to scheduling. I have ages 13-18, plus one who is 23. My tap 3 has really picked it up well. Basically they all know the basics so we work on variations of steps and speed. What I do is do everything at a moderate speed, then at a fast speed. That allows my 3s to get it at moderate, but my 4s to be pushed. Going at a moderate speed first aint gonna hurt 'em .
Example: if we are going across the floor doing maxiford turns, my threes go at a moderate speed and then add a pickup, my 4s always do a pickup and go faster.
The only drawback is music. Its hard to use with this class, because when I get it fast enough for moderate speed, then its way to fast for a fast speed (we arent double timing it).
My students don't mind the age difference.

I find tap the hardest to combine because you are working with sounds and rhythms. When you have jazz, ballet, and other, you can still do things in the same counts but they don't interfere because you don't "HEAR" the steps.

I had this issue at a job, where they kept introducing kids with little experience, with kids who I finally got up to a certain level and would even push some lower level kids to a level above mine, to the dismay of that teacher. Very frustrating.

Can you get an assistant? Then you could lead steps with the higher level kids as she/he does with the lower level kids.

If not, take the warm ups and combinations and blend the levels. Start with the simpler version and then add to it.

Thanks for the suggestions, the class begins in 2 weeks so I have a lot of time to plan, I just hope they all stick with it, I would hate to loose any of them due to this.
An assistant would help of course but not really possible, myself and the SO are the only teachers on the school, 2 of the seniors student teach but are only 14 and 16, the same age as half the class, 1 is even in the class so not really doable.