How many of you DM for more than one table? If you do, how many tables do you run?

This Academic year I’ll be running four tables. Because I live in a small town, I’ll be running all four of them and we don’t have any other DM’s. I am in the process of growing a few of the players into it, but most of them are new, and even the one who has DM’ed before is still very new to it.

I will be running a game every Sunday and Wednesday. Every other week will be the alternating groups.

I have a total of 21 players who want to play, so parties of 4-6. 7 of those 21 have been playing with me for a year-long campaign that took them to level 6, so they know the ropes at least. They’ll split into two tables (a scheduling necessity) and each run the same content. But the other 14 are mostly brand-spankin new to the game. I teach the game fairly well, so I’m not looking for advice on that.

I’m asking for advice: how can I run four tables and not spend twenty hours in prep time per week? I’ll be running 2 per week, 4 games per month per table. How do you prep to save time? What cool multi-table elements have you seen work well? I still want the narrative to be compelling, so I don’t just want to run straight from a module with no adjustments. What things am I not asking that I should know?

Thanks in advance y’all!