Everybody knows Oregon Trail. It was a mainstay on Elementary School computers, and a perfectly grim time-waster with educational elements. Really, looking back at it now, we're not totally sure how this game was educational. Maybe it was trying to teach us that traveling the Oregon Trail would've been terrible.
Oregon Trail was an adventure game, an action game, and the true predecessor to rogue-like randomly generated, painfully difficult games like FTL. You pick your character, select your provisions, and attempt to ride the Oregon Trail without dying of dysentery. The game is so ubiquitous, it's basically the Mario of educational games. When you think of Back-To-School gaming, the first thing I think of is Oregon Trail.