«Experiments have been carried out on so-called propaedeutic Esperanto, i.e. the theory that teaching of Esperanto to first-year language learners, before they embark upon (for example) French or English, makes the learning of these languages more effective. What Helmar Frank's research at Paderborn and for the San Marino International Academy of Sciences shows is that one year of Esperanto in school, which produces a communication ability equivalent to what the average pupil reaches in other European languages after six to seven years of study, accelerates and improves the learning of other languages after Esperanto. The propaedeutic value of Esperanto was described for the first time by Antoni Grabowski in an article of 1908.»
If you want to read more about it, just click in this Wikipedia link Propaedeutic value of Esperanto
