There's actually a better method to lock calculators with the TI-Nspires, I own one myself.
By pressing a certain key combination, you activate a mode called "Press-to-test". What it does is that it locks all of your documents in the calculator so that the student cannot access them during the middle of tests. Other functions such as geometry functions can be disabled as well.
A handy little LED light blinks at the front of the calculator to indicate it is indeed in Press-to-test mode. The mode can then be deactivated later by connecting the TI-Nspire to a computer and sending a file, or by connecting it to another TI-Nspire. Key code combinations and additional info are in the link below. ^.^
Source: http://education.ti.com/en-GB/uk/products/ti-nspire/ti-nspire-cx-handheld/exam-acceptance/press-to-test
But to be honest, clearing the RAM on students' calculators only wipes the memory that they happened to not have archived, fyi. If they archived any programs, ex. some with some handy little notes, it will not be wiped and will be available to use after unarchiving it. There also happens to be a press-to-test mode for TI-84s as well, that does the same function as above.
http://education.ti.com/sites/US/downloads/pdf/press_to_test_ti84p.pdf
https://epsstore.ti.com/OA_HTML/csksxvm.jsp?nSetId=99820
Katrina R. (guest) 13 Feb 2014 18:38