Provably, temporary, disable wireless networking on Android tablet I am taking an exam during which any materials or electronic devices are allowed, provided that I can demonstrate that they cannot be used for communicating with others. I want to take my Android tablet and use it to display PDF files that I don't want to print out.

I need to come up with a way how to temporary turn a Nexus 7 Android tablet from a communication device into a book reader incapable of connecting to WiFi. I need to be able to quickly prove to the teacher that this is so and that whatever I do it will remain in this mode during the exam.

Do you have any ideas how this can be achieved? My belief is that this is impossible, but I decided to ask anyway.
As no "bullet-proof" system is required here, and at least some level of trust assumed, possible solutions hide behind the buzz... ahem, key-words kiosk-mode and child-protection. In short: you create a "jail" you're working in, and hand it's key (password) to the teacher (let him/her set a password – of course on the premise to unlock you once the exam is over).

Options on establishing a kiosk-mode are already discussed in several other questions tagged "kiosk-mode", so there's no need to repeat them all. You might wish to take a look at SureLock Kiosk Lockdown, which should meet your requirements: one of its features is to prevent access to system settings. So disabling all network features (mobile data, WiFi APNs, etc.) and then locking the settings with the teacher's password should satisfy both sides – provided you've allowed all required apps for kiosk mode. As the "dirty trick" to regain control would also remove all data from the device (factory-reset), it cannot be expected you'd do that during the exam ;)