Make it very easy for you, the principal and everyone else.
Just pick a regular Victorinox Explorer
http://www.swissarmy.com/MultiTools/Pages/Product.aspx?category=outdoor&product=53791&
Show it to the principal and ask if you could carry that instead. Then you and him are clear on exactly what knife you are using.
Yes, it has no clip but why a clip. I have an extremely hard time understanding the knife laws over there. If you are only allowed to carry a knife with a clip, why dont just carry in in a sheath then. Even Stupid and his brother can see that you hava a knife, or at least something with a clip that looks exactly like the knife has has at home.
By the way, if you are allowed to carry a multitool, why do you need an extra folder?
I have carried several knives and multis since I was 15. Most of the time it was a SAK. people knew about it but did not hassle about it. In theory you are not allowed to carry a knife at school in sweden too. However it usually depends on who and what. The straight-A student with a practical SAK will pass while the "cool" dudes showing off their knives will be liberated from them instantly.
Both the SAK and any multi, like the old LM PST, are by almost anyone seen as a tool that has a knife on it, together with screwdrivers, tweezers and what not. That "tool" can do many more things than just cut things, it can improve living in many more ways than just a folder.
The SAK has almost become the "standard" when it comes to legislations and knife laws. Many laws are written so that it allows a SAK but not above that. Since the SAK is a such well known concept it makes it easier for the enforcement as well. Red gadgety knife thing, OK. strange black thing, NO.
So I suggest that you try to negotiate that he looses the clip requirement, that would certainly reduce the possible "fuss" about you carrying a knife. Look at the people you meet in a day, can you tell if they carry a small pocket knife in their pockets or not, maybe it is their keys or a cell phone or a chap stick or whatever. Those people with a clip in their pocket is surely carrying a knife.
Lets compare it to something else. You walk past a lot of girls, some might be married, you dont know who. However all girls with a wedding ring are married, those without a ring can be either. The symbolism doesnt work both ways. If you have a clip in your pocket you are carrying a knife, if you dont have a clip, noone knows, you might, you might not, and since the default is not that you probably assume that they are not carrying a knife, but then there comes this guy with a clip, that stands out like a different looking whatever.