Crafting Fractions world is inescapable???

The "Crafting Fractions" world is inescapable. I tried it last night before using it as a lesson and created my 18 ladders, and first, could not find where to place them on the wall.. Finally I found multiple possibilities, but then couldn't go over the wall once it was built, and by then I'd used all my ladders. I switched to creative mode and still could not figure out where exactly the ladders were supposed to be placed, although I did eventually find a hole out and above the world. 

I warned my class of Grade 7/8/9 students that I had the issue and challenged them to figure it out because they know a lot more than I do, and not a single one could figure out how to actually escape the room either. 

ARE WE MISSING SOMETHING?