Easy to do. There are several tasks that a teacher can easily just wordprocess and give the students in a file to work on in some way on the wordprocessor. A text with words missed out to be filled in A text with inflections like - s missed off the words to be filled in See a collection of such suggestions at various levels. Text can be long or short. It can even be disconnected sentences if preferred.
Students can work independently or in groups, etc.
This is of course in addition to the possible use of WP as part of a regime of composition writing, to encourage redrafting, revision etc. Requires only WP expertise, and no need for Internet access. The WWW contains lots of CALL material, both intended as such and not. But the problem with the WWW for students learning English is to rapidly find a suitable CALL task or exercise. In fact that is the problem with using the WWW in general.