[bread_baker]

That fluid class is so typical in California adult education!
Ask the school if they can limit the new people to only starting on Mondays, instead of any day of the week. This will help you a little bit. I like to start new units on Mondays.
You will need to collect a bunch of review activitites, so that you can teach the same content again, but with different activities.
I'd also figure out who the high students are, and ask them to help the newcomers.