I guess I'm a little confused on what exactly you are needing. If you already have the 10 workstations, are you only looking for a server for integrating with those workstations? What do you want to do with the server, group storage, domain controller, application server? If you already have the workstations what operating system are they running? What kind of usage are you intending for these computers - basic internet access and an occasional typed document?
If you don't have the individual workstations, then what kind of end user experience are you planning to offer. In other words, do you have to go with a Windows desktop, or do you need to offer something like Linux to keep the costs down?
There are a couple ways to approach this, but it's hard to tell exactly what you want the server or the end computers to do, so it's hard to make a recommendation for the specific situation, but here's a couple options:
Option 1: Virtualized desktop environment. Set up a server running Windows Server and configure it for terminal services. You can then set up your individual workstations to just remote desktop to the server to get their actual working environment. This makes configuration easier as you only have to install your necessary software on the terminal server. Additionally, your workstation computers don't have to be anything fancy. You can use very cheap or even older repurposed computers to handle the remote desktop session. The performance isn't going to be spectacular, and depending again upon the performance and purpose you are planning for these computers it may not be ideal, but it's one way of accomplishing this type of computer lab pretty cheap and easy starting from scratch.
Option 2: Windows Multipoint Server 2011. This version of Windows Server allows you to connect multiple monitors/keyboards or remote desktop or special thin client to a single server and operate multiple remote sessions with ease. It has advantages and disadvantages to doing a terminal server, and you'd need to talk with a professional directly in regards to the specifics of how you want to run the lab environment, the expected usage and performance, and the available budget.
I guess the big question for me is are you looking to get just the server because you already have the workstations, or are you needing to get everything including workstations still.