This is a big revision of a previous post of an idea. The previous post explained the idea poorly.
There's been several attempts to create a universal language (for example, Esperanto). Unfortunately, no one has adopted them.
Also, any successful universal language would suffer Babylonization
just like all other human languages. Take Latin; at one time it was a standard throughout the mediterranean; now it has branched out into Spanish, French, Italian, etc.
Now, if someone wants to study English, they have to decide: American or British? There aren't major differences now, but they will continue to diversify until they are mutually unintelligible. Also, a non-English speaker must study different dialects of English if they want to understand, say, an Irish person, a Scottish person, a Jamacan, and Indian, an Austrailian.
I spoke with foreigners learning English and they say it's not as easy to pick up these dialects as you might think.
In fact, in the 1930s, American films shown in Britain had subtitles, because Brits had never heard American accents before, and couldn't understand the films!
Human languages quickly develop into dialects which then turn into new languages. This is a problem with any human-taught universal language.
However, your average human child under 13 can learn any language in about 6 months in a total immesion scenario. The human brain is just wired to pick up language at that age. It doesn't take any special training or classes; just normal, everyday conversation.
I propose that once we get a robot or computer that can carry on a conversation well enough, we create an endeavour to install such machines in every classroom in the world.
These machines would all converse in the same language. It doesn't matter which one, so long as they all speak it identically, grammar and vocabulary.
This would require any special classes or anything, just have the kids carry on a conversation for some time each day with the machine.
All kids exposed to this machine at a young age will then be able to communicate with any other kid with the same experience.
Since machines are the conversation partners, there is no need to worry about dialectization, because we keep the exact same standard language in each machine.
Kids would continue to speak their native languages at home, at school, in their country, wherever. They would continue to learn foreign languages.
All this does is add an extra universal language that all people would be able use.