Version 3 update:
-Improved Printability... the castle and pen topper still need support on when printing, and the flag is VERY fragile (I broke half of mine removing support), and some of the windows are still too thin. Stay tuned for version 4.
-Reduced Sizes... so now they fit on a standard build plate at full size. The castle is still a beast to print, took 10+ hours with 0.2 layers and 10% fill on a rep2x.
-Improved Strength... Catapult mount is now sturdy (but still needs some work), and the lid slots firmly into place.
-Minor cosmetic improvments... Added tick marks to the ruler amongst other things.
-Also check out... My related "Gnome remix Challenge" entry: "The Castle Gnome"... T.B.A.

This is my entry for the back to school challenge... this is still a work in progress, but already fun :D final dimensions are still subject to minor change.

The Castle School Set contains:

• pencil case: "The Castle Case"
• ruler: "The Catapult"
• pencil topper: "The Tower Topper"

"The Castle Case"
Get down low... lower... right down to the table. Now look up at the imposing majesty of the Castle Case, with patented catapult mounts (now powerfull enough to launch projectiles printed with 100% infill), retractable roof and missing portcullis. Defend your desk in style with four pencil sized tower topper slots.

"The Catapult"
Rain down powerful artillery attacks near and far. "The Catapult" can be connected to the Castle Case to extend range and alter the angle of attack... it also serves to measure out about 15cm or there abouts.

"The Tower Topper"
Make your castle your own by selecting four very special pencils to support your four towers and decorate your Castle Case with towers and flags. Now with optional "Gnome Castle King": http://www.thingiverse.com/thing:151032

This is now my third draft and things are coming together nicely. Suggestions always welcome but future plans already include:
-still thicker walls
-add ruler numbering to catapult
-modified catapult rocker with inner ring to mount castle.
-make flag even more printer friendly... angled up maybe?
-exagerate some feaures on towers
-brickwork
-fix second level balcony
-archways
-porticulus
-army :p