When logging onto Window 7 computers they tend to show the name of the last user. Yes, there is an option to switch to Other User but this can be a bit difficult for younger students to figure out. Fortunatly there is a way to set the computer to always want a fresh log in. Here is how to do it:
In run enter secpol.msc
Open Local Policies
Open Security Options
Find Interactive Logon: Do Not Display Last Users Name
Open and enable that.
Now the computer will always ask for log in information.