Which toolbar? You can do it with a macro:
CommandBars("Menu Bar").Protection=msoBarNoMove+msoBarNoCustomize
CommandBars("Standard").Protection=msoBarNoMove+msoBarNoCustomize
CommandBars("Formatting").Protection=msoBarNoMove+msoBarNoCustomize
The help on the Protection property lists the other types of protection you could apply... adding the constants.
Say, msoBarNoChangeVisible to prevent hiding a toolbar.
If you want to teach how to customize Word, you'd need to remove the protection, though