World language?

Well Ive been wondering; what would be the effect of a world language (Also Im doing a study about the affect a world language would have). It would replace ordinary second language in schools untill all educated people could read and write in it. What are your views?

Considering the size of the world you would end up with dialects so different they would baiscally turn into new languages. This is already the case in many nations, personally I sometimes have trouble understanding people from the other side of my country, and I live in a small country.