Yes and it lives up to that promise. This article says English is "easy" but Esperanto is so much easier you can learn it for free along the way of learning English.
> The tests were completed by the pupils who learned Esperanto and a control group of equal size and same previous language learning experience, who did not. They showed that the children who participated in Multilingualism Accelerator classes had considerably higher scores than those who didn't.
Lots of my friends are Esperanto speakers and we use only Esperanto to communicate. I learned it to fluency in around 2 years. It’s incredibly easy to learn, super fun to use, and unique in that it bridges so many other languages that one can really experience a lot of different culture through the language.
For an overview: https://en.wikipedia.org/wiki/Propaedeutic_value_of_Esperant...
And a recent experiment: https://ec.europa.eu/programmes/erasmus-plus/projects/eplus-...
> The tests were completed by the pupils who learned Esperanto and a control group of equal size and same previous language learning experience, who did not. They showed that the children who participated in Multilingualism Accelerator classes had considerably higher scores than those who didn't.