When a homework is due you will turn it in during your "class" that day. SO we have a representative "class post" made by teachers on the day of the class. For example, if your transfiguration essay were due on Thursday, January 6th, McGonagall will put up a post on that very Thursday (in the community) that simply says:
THURSDAY (Jan 6th) TRANSFIGURATION CLASS
Gryffindor/Slytherin
This "class" encompasses all years, 1st through 7th unless specifically stated by the teacher that the classes fall on different days for different years/houses... because, well, it would be very hard to work out everyone's schedule.
You post your homework as a comment to this entry.
The teacher will post your grade, as well as comments and corrections *laughs* on a comment to your comment with your homework.