We're about to set a Computer Lab for training porpouses, in this training session some of the times we will need the students to see what the teacher is doing in a single computer (lets say the server) but we need them to see it at their own workstations. I saw several years ago a software that allows me to do so, but i don't know the name. But I guess should be several programs to achive that.

i case that I'm not being very explicit, let me show you an example

I have 5 computers in the lab, 1 server (the teacher computer) 4 workstations, in some point the teacher runs this software and take control of the other 4 workstations. then every body in the room has the same screen, the teacher's screen. The teacher runs word, and every body see the word splash screen, the teacher writes "Hello world" and every body sees the same words in the screen, go it?