The emphasis of the Schools Council Research and Development Project at the University of Wales on teaching English to Welsh pupils aged 8-13 was on curriculum development. This paper covers the problem of acquiring the necessary basic knowledge about the needs of Welsh first language pupils in the learning of English when long-term, rigorous research studies are not possible. About 250 teachers throughout Wales completed surveys by filling in questionnaires on errors made by pupils, methods of teaching English, language textbooks in use, pupils' interests and popular reading, and all information was channelled into the preparation of classroom materials. The limitations of asking teachers to report their pupils' errors were taken into account, but useful information was gained about the influence of the Welsh language on English spelling and sentence patterns. Responses were least helpful in those areas which cause confusion among teachers, most notably idioms and spoken English. The greatest problem for teachers was the question of standards in oral work. Such limited surveys for specific purposes were found to be valuable in indicating the size and complexity of language learning and teaching problems, and also in showing the need for further teachers in-service language work, with courses in linguistics or language in education. (Author/MHP)