Grammar teaching could be surreptitious, as it were, with a clear underlying theory of grammar but minimal use of grammatical terminology. This is in fact how a lot of grammar teaching has been done; and in particular there is a well-recognised activity called 'sentence combining' which seems to be widely used in the USA. There is some evidence, apparently good, that this kind of activity benefits children's writing (Abrahamson 1977; Barton 1997; Hillocks 1986; Mellon 1969; O'Hare 1973), and in some studies it turned out that this kind of grammar teaching produced better results than more traditional teaching of grammatical analysis. For example, " Hillocks surveys the many studies of the effects of sentence combining, and finds them overwhelmingly POSITIVE at all levels (grade 2 to adult). 60% show significant gains in syntactic maturity; 30% non-significant gains; 10% no gains." (Weaver 1996, reporting Hillocks (1986)).