Password protecting from within ftp…

Hi,

I have a client who has bought a virtual hosting plan with one ftp account. However, she wants an several classes full of students to be able to access the ftp under restricted permissions. Is there any way to password protect directories so that even though all of the students will be using the same actual account, they must know a password for each directory, prohibiting their accessing other students’ work?

Most thankfully,
Luke