|We get students wanting their home work done for them :-)|
Have you google workgroup vs domain so you can get a side by side comparison?
First question to consider are how many workstations do you presently have and what is your existing infrastructure.
Second is what applications are you running.
Third is what will a domain offer you, that you need, that a workgroup can't do.
With this information it can be determined the best course of action.