While a few students who were unable to learn via the oralist method were taught with signs, many students preferred to communicate with each other via sign language, sometimes to the frustration of their teachers. The first study of the sign language of these children, which is almost certainly related to modern IPSL, was in 1928 by British teacher H. C. Banerjee. She visited three residential schools for deaf children, at Dacca, Barisal and Calcutta, observing that "in all these schools the teachers have discouraged the growth of the sign language, which in spite of this official disapproval, has grown and flourished." She compared sign vocabularies at the different schools and described the signs in words in an appendix.