Switching computers to have its net connection?

Hi guys, i just want to ask a noobie question. Is there anyway that i can do this? I have 2 computers it would 3 in the couple of weeks 1 for me, the other for my eldest son and the next would be for my youngest son.

What i wanted to do is have a switch which will control internet connection, lets say i want the computer 1 to have internet connection because comp2 and 3 is off, or turn on internet on comp3 and disable net on comp1 and comp2 or turn on all the internet connections on the 3?

Yeah i know why not just leave it on the router? whats the deal of turning the other computer off? Well my point is that in our country Philippines aside from corrupt government officials we also have corrupt companies or internet providers who provides expensive and slow internet connection. So if all the 3 is connected my connection is greatly slowed down yeah i know because the connection is being split what i meant is that when all 3 is connected even if the other 2 where turned off its still slow and sometimes i lost the connection so sometimes i unplug the lan at the back of the other computer, put the lan network directly to the isp router and just put it again if i want to use the other computers and by doing this i have wasted a lot of net cables and i always buy another so just to make my life easier and not to spend more.

How am i able to do this?   thanks a lot.. I have 1 isp router connects it to 4 port edimax router, so what i always do if i want to use computer and have max connection i unplug the others and put the cable directly to the isp.

Ok thanks for reading my thread, im not sure if i have explained it well. Pls help