Well, I save the game in "Na" but by error I saved in "Co" and I have no idea about how to delete a file >.<
So tell me if it is possible :3

And the other one...What's the better way to clear the ALAP school level? I'm not sure, so here is how I try to clear it:
I start on the table with all these papers and ink (the japanese calligraphy), and when I get all the table you go to the next table crossing by the brooms, and getting some things of that table, then I go down, and when I'm about 37 cm, I go and get all those buckets. Then, I roll up some things on the floor, and when I'm 50 cm, I go to the corridor, and start rolling some things. Then, I go to the bathroom, I get all the toilet paper, and go out of the toilet. Then, I go to the teacher's lounge, I roll up everything on the tables. Here is when I clear the level, sometimes in the next room, the first classroom on the beginning of the corridor. I roll up everything I can on that room, and then I return to the first class and roll up everything. But then the time is over, and I get about 3m 50 cm. I want more!
PD: Sorry if any spelling or gramatical mistake, remember I'm Spanish ^^U

you would have to completely delete your save file for the Co file to disappear I believe.

I can't really help out very well in level walkthroughs since that's not much of my specialty but this should help you: video in database

You don't need to delete the CO savegame, when the save file is created, it has room for all the three saves (NA, M, CO). It takes as many memory blocks if there's only the NA-save, or if there are saves in all three.

i always made two save files on purpose. i like having backup copies around when possible!
maybe just leave it there, it could come in handy if your main file gets damaged, or overwritten by accident or whatever.

for my biggest run, i didn't sweat the little things like you have to do in some other levels. since you dont' ever get so big that they disappear.

The route i take is pretty similar to the one you mentioned, so stick with that. When you get back to the room you started in, don't try to get every kid first time through, just make a quick run at it and head next door. once the middle classroom is pretty empty, you should be able to get the walls and start to really get everything in sight.

Hope that helps get you up there!

chris