Need spy software for real time surveillance ?

I need a software which will let me spectate what is done on the other PCs in my network in real time. I can put a file into the other computer if necessary. I want something like a Remote Control. The thing is do not want to control the other PC but I want to see what is done on the other computer i.e. I want something like in the schools, the teacher can see everything that is done on that computer. Could you tell me the software?