Wow...loved so many of the ideas that I'm going to copy/paste them and take them with me...THANK YOU!!!
I am actually certified to sub for grades K-12 but because of my years of volunteering, the principal at my boys' school have already inquired about subbing there. I am not sure if I'm ready to jump into high school...some of those kids are probably more intelligent than I am...LOL!
You're welcome!
I remembered what I forgot to add earlier. My experience subbing was primarily in city schools, and one of the districts did not require teachers to leave plans, so I rarely had them. I could never count on being able to find materials either, so I traveled with my own supply of the basics: pencils, crayons, blank paper (copy and lined). Hopefully, you won't need to use it, because then you won't need to keep refilling your supply.
With those basics, you can have them do writing (free write, to a prompt, or a book review) and illustrating. You can do dictation or math problems.
Name Collection Boxes: give a number and have them generate as many "names" for that number as possible. For example: 10
ten, diez, ten tally marks, 10 stars, a dime picture
2+8, ,8+2, 1+9, 9+1, 10+0, 10-0, 100-90, 10x1, 100/10, etc
And good luck! You are lucky that you are already familiar with at least one school. That can make a huge difference; you already know who you can ask for help and the basic routines of the place.