Instead of exposing students to Windows kernel code[1], it would be better to consider to read the ReactOS source code - an open source clean room re-implementation:
Over at the Wine project, we forbid contributions from anyone known to have looked at Windows source code or even done significant "white box" reverse-engineering (decompiling, etc). The intellectual property law landscape is far too frightening to be worth the risk of allowing contributions from "tainted" individuals.
Statements like these are "legally reassuring" but it's very likely that you can get the same functionality but implemented very differently even if you looked at Windows' code. In the end it's probably another thing like piracy: everyone does it, but few would admit.
Additionally the books for user mode programming from Jeffrey Richter and Charles Petzold tend to be quite good and full of valuable information as well.
Read the comment above by coldpie about WineHQ project. The same is true for the ReactOS project.
In 2006, an overenthusiastic contributor caused troubles. The aftermath slash back the project for several months and stressed the relationship with Wine for some time. Since then, every possible effort is made to keep the code clean and disallow tainted developers. (that's why I wrote the comment above, to warn others) You can read a short summary on Wikipedia: http://en.wikipedia.org/wiki/ReactOS#Internal_audit
http://www.reactos.org
[1] signing such an NDA will prevent them from contributing to various open source projects, that would be a shame.