There is an unpublished report on The Development of Language Learning Aptitude and Metalinguistic Awareness in Primary-School Children: A Classroom Study. (Tellier, Angela and Roehr-Brackin, Karen – 2013 – The Development of Language Learning Aptitude and Metalinguistic Awareness in Primary-School Children: A Classroom Study. Discussion Paper. Essex Research Reports in Linguistics, University of Essex, Colchester, UK.)
This is taken from the abstract:
We examined whether the teaching and learning of either Esperanto or French would facilitate the development of language learning aptitude and metalinguistic awareness in 8-9-year-old children (N=28), thus setting the scene for enhanced explicit learning even at a young age. Following instruction in either Esperanto or French over a school year, children made significant gains on measures of aptitude, metalinguistic awareness, and L2 proficiency. Effect sizes in the Esperanto group were larger throughout, however, with greater homogeneity of performance in evidence and a closer association between aptitude, metalinguistic awareness, and L2 proficiency at the end of the treatment.
It gives quite a detailed description of their classroom experience.