· Give students a mode for self-expression, creative thought, musing
· force students to read assignments by deadline
· make students active learners.
· help students push deeper into a subject
· enhance storage of information, understanding, recall
· teach students some things about writing:
· focus, organization, evidence, style
· conventions of writing in a particular discipline
· polish in spelling, punctuation, grammar
· Provide feedback for the instructor
· basis for grading
· find out who needs help
· provides a way to track class progress in order to help with planning.
 

from: Helping Students Write Well   2nd Edition, Barbara E. Fassler Walvoord