Although there already is a great school entry, my kids (6 and 9) and I came up with this one, which is a different concept from the other entry.
(Sorry for the not-so-great image quality, but it's my first MOC, so bear with me!)
Here is the complete set -- a snow-covered traditional one-room schoolhouse, with bell tower. Seven minifigures (teacher, bus driver, janitor and 4 kids) plus a school bus, bench with light post, and a little toboggan.
Here is a better look at the schoolhouse itself. The design is typical for New England one room schoolhouses. The red diverges a bit from the official sets but is iconic for this building in the U.S. I went with the heavy snow style construction. Note the light brick at the base of the chimney, whch lights the fire inside.
Next is the bus. It fits three kids plus the driver. Notable features include a brick-built working door and a brick-built stop sign, which deploys when kids are loading and unloading. Please kindly ignore the fact that I did not push one of the bricks all the way down!
Here is the first interior shot. At the front of the room, the teacher is working with the students on simple counting at the blackboard. I had a checkerboard tile pattern on the floor at first, but the only 2x2s I had on hand in sufficient quantity were red, and it was a little too much red!
And here is the rest of the classroom. The books on the shelf were created by my son; I think they look quite nice! The Lego kids don't really sit, since their legs dont ben, but I have given them chairs anyway. You can see the warm fire in the background (I hope!).
The rest of the photos are here.
Although I harbor no illusions of winning given the many other higher-quality entries, building this with my kids was a lot of fun -- and that's what the hobby is all about! Thanks all for inspiring us to jump into MOCing...