@kidsfuture It's an interesting idea, although I must confess to being a little ambivalent personally about Esperanto, having tried to learn it years ago when my dad first mentioned it to me.
I think the principle of a universal language is an excellent one but I'm not entirely sure that a synthetic language is the answer in the short-term. Apart from anything else, by the time you have enough teachers trained to teach it, won't many of those children have moved on? (Disclosure - I'm a trained modern foreign languages teacher, though I chose not to go into teaching as such at the end of the course, so I have some understanding of how difficult it is to communicate in a language not your own, even when the root languages are related.)
My other languages are a bit rusty these days round the spoken word; for now, thanks to history, English remains the main language of science, medicine, technology, and airline travel, amongst other subject areas. If America had gone down a different path or two, of course, or hadn't become the most powerful country on the planet, the international language could equally have been French or Spanish or Dutch or German or several others....
As English is such a "Heinz 57" language, with such a hotchpotch of influences, I've often found if I'm in a country where I don't speak the main language and the Roman alphabet is used, if I write down what I need to know or buy, between us we can usually work it out. Does Esperanto currently have the terms required to discuss environmental issues, not just loan words from the English, or the French, or the Kiswahili, just throwing them in there as examples?
I'm genuinely interested, as my understanding was that the Esperanto movement ground to a halt some time in the 1970s. So using it as a discussion medium may mean that all parties are then having to discuss serious issues in a second (or third, or fourth) language that may or may not have the vocabulary required. I'm not sure that would get the message across as clearly as it needs to be communicated either, but I don't know what the answer is.