"I teach 2nd. year students at a technical college"

Designing & Building a GSM terminal from scratch is most certainly not a 2nd year college project!!!! :-0

You are talking about a major project with probably hundreds of man-years of effort for experienced graduates!

You need to buy a GSM module, or a phone with a suitable interface.

The command set is specified by ETSI; I've given the links here before - use the 'Search' button.

You will, of course, also have to read the Manual for your chosen GSM module(s).

BTW: There was an article about an 8051-controlled Wavecom GSM module for SMS in Elektor the other month.

There's lots of stuff on the web.