I could go on and on about the food, water, shelter, and disease problems we'll be up against, but let's put that aside for now and focus only on the transmitting information part.
My first thought was using berry stains on rocks to record anything useful, like the alphabet. But that's unlikely to work since any berries will be used as food, not ink. Someone suggested charcoal, but that may not be easy to find depending on where you are. A sharp rock may be your best bet - it can be used as a tool and as something to write with.
Once you got your writing implement, what would you write? Just the basics of electricity, mining, math, programming, and manufacturing could easily fill several textbooks. Unless you have a mile-long cave nearby, you can only write down the equivalent of maybe a dozen pages of text, formulas, and drawings. Anything exposed to the elements will wear down quickly and be unreadable in a matter of months.
Also, the math involved in finding those giant prime numbers is quite complex. It isn't just dividing numbers by other numbers. Look up fast fourier transforms (FFTs), zero padding of FFTs, and the Lucas-Lehmer-Riesel test to get an idea of what is involved. What are the odds that at least one of the survivors will have any clue on what those things are?
Now we get to the teaching part. First of all, how much of the stuff that you learned in high school do you remember? If all you had were a page or two of barely legible notes, would you even be able to pass a high school trig or programming test if you took that class before but haven't used that material in decades? And how are you going to get the next generation to care? This is what you'll be hearing:
"I want to climb some trees, but Daddy says that learning what all these weird symbols mean will eventually bring back something that you can ride on and fly across the ocean. It's like a dragon that you can safely climb into, and it never gets tired. I'll go listen to what else he says. See you tomorrow!"
"Yeah, I heard that story too. The big guys also told me that there are things that run on this invisible force they call electricity. They say we can use it to instantly talk to people that are thousands of miles away."
"But what's the point, guys? Even if what they're saying were real, do you think any of that's going to be coming back in our lifetime?"
"You're right. A lot of those older guys seem really weird anyway. Hey, look! A squirrel! We're going to have a nice dinner today!"