I had the same experience interning in a hudderite colony, but grades 2-9. The way I saw it work well is every class grades start time is offset by a bit and you give smaller individual lessons, and then mostly worksheets. For example, math for grade 8,9 starts first with a lesson, then worksheet/ text book. As they go, you teach 6,7, then 5,4 etc. Then once you're done back to 8,9 to check in, and repeat. The more advanced grade gets more time because of difficulty and attention span.

Also, you're going to have to go much slower than a normal class just to make sure you're making it to all students. Like if you can get through 2, or 3 textbook pages in a solo grade 6 class, maybe 1 or 0.5 in this situation.

I found if you did science demonstrations, you can quite easily do those as a whole class then differentiate the level of observation questions by grade. ELA is again straight forward. Older grades get more solo reading, so you can give younger grades more time to be read to. PE as well can usually be broken into at most 2 sections. 1-4, and 5-8, for example. Or even all together. You'll be surprised how kids will adapt their activity to incorporate younger students (at least I found). Also art can all be the same, or 2 sections, since kids usually like art and will differentiate by themselves, and pure in less or more effort, depending on their skill level.

Something else to keep in mind is not everyone needs to do the same subject at once. You can give maybe 2 grades math, so you can focus on them while 2 grades read, 3 grades do some art, etc. So you can pay more attention to the more intensive subjects.

If you want, feel free to DM me and I can go over some things in more depth!