Conclusion
In conclusion, the idea that grammar teaching improves children's writing skills is much better supported by the available research than is commonly supposed. However there is no denying the need for more research in this area, so we finish with quotations (from Walmsley 1984) by two of the twentieth century's most distinguished psychologists who have taken an interest in this question. First, Robert Thouless (1969:211):
"If a small part of the research effort that has been put into demonstrating the uselessness of grammar ... had been distributed over a wider field, more might be known about how skill in the use of English can best be developed."
And second John Carroll (1958:324):
"I am reasonably sure that unless the student gets a feeling for sentence patterning ... his own sentence patterns will show many obvious defects. Research on the effectiveness of teaching English grammar in improving English composition has been mainly negative, but until this research has been repeated with improved methods of teaching English grammar, I will remain unconvinced that grammar is useless in this respect."