Basic Mouse is a cheap shareware application with trial mode which enables you to block or redirect clicks of the right-mouse button.
The software also includes functions to block keystrokes and create a kiosk mode which 'traps' users inside a particular application.
This is a very useful app for the very young or users with motor difficulties which cause them to accidently click the right-mouse button.
The additional locks can also be useful tool to keep students on task.