First, decide on what the purpose for the site to be - is it going to be more of an online handbook with policies and contact information or is it something that is to be used actively by students and parents?
If it is going to be used actively you will need to keep it updated regularly - at least once a week. Since this is for an assignment, I'll assume that the purpose and what should be on there has been assigned to you.
Next, you will want to look at free services. Some that are popular with teachers:
www.schoolrack.com
www.classjump.com
www.weebly.com
You might also want to consider
www.wordpress.com - it is a blog, but allows for multimedia hosting, 3 gigs of storage and it is also free.
You also might want to go out to one of those services, but together a trial run, and then post the link. I'm sure people would be happy to give you pointers once you have something to start with.
Happy web-building
