It's hard not to find something educational in Epcot or Animal Kingdom. Each pavilion teaches you something different...some better than others. Personally, I'd recommend Universe of Energy (fun, funny, and educational), Circle of Life, Living with the Land, the various exhibits in the Seas, and parts of Innoventions. The films of the various countries are incredibly educational about their people, landscapes, and cultures. And for a real history lesson, as mentioned by KHockett, you can't beat American Adventure or Hall of Presidents (at the Magic Kingdom...yup, you can learn a lot there, too!).
Animal Kingdom has lots of good information about - of course - animals and the environment. I found Rafiki's Planet Watch to be a great source of information, as well as the Kilamanjaro Safaris, Pocahontas and Her Forest Friends, all of the nature trails, and even Flights of Wonder drops a nugget of information once in a while. Flights is more fluff than substance, but worth a try.
Disney-MGM is educational in a different way, showing aspects of how films and television are made, though in recent years the educational aspect has been downplayed significantly in favor of cheap thrills.
I'm always amazed at how much information I pick up at the Disney MParks and am able to use later. There's enough there to write a hundred reports, all on different topics!