When shopping for a new TV, things you might want to consider.

Is it cable ready? Most are these days but if you get one that is not, you will not receive all of your school channels.
Do I need audio and video inputs and outputs? These are features that add functionality but also to the cost.
Can I operate all the functions on the set without the remote? Remotes get lost and you don't want to be stuck because you don't have one.

When it comes time for service, you will receive the fastest turnaround on sets that have local parts available. Currently this includes RCA, GE, Proscan, NAP, Magnavox, Zenith, and Panasonic. Slightly longer availability includes Sony, Sharp, JVC, Toshiba, Samsung, and Hitachi. I can get parts for others but
turnaround becomes much longer. Mitsubishi is probably the worst company to get parts for.

TV/VCR combinations are not a good idea. If one portion fails, you loose both!

Should I by a HDTV? All the CCTV systems in our schools currently operate on the NTSC standard. See Things you can use to learn about HDTV.