The effect of grammar teaching (sentence combining) in English on 5 to 16 year olds' accuracy and quality in written composition

4,691 papers screened; 267 full papers re-screened; 64 met criteria for the systematic map; 20 papers reporting 18 studies entered the in-depth review

English-medium schooling nominally ages 5-16. In practice, "all but two of the studies specify the age group they worked with: predominantly, this group ranged from fourth grade (9-10 year olds) to tenth grade (15-16 year olds), with the majority clustering in the upper years of primary/elementary schooling and the lower years of secondary schooling." 17 of the 18 studies were from the USA, one from Canada.

EPPI-Centre systematic review, protocol peer-reviewed and published in advance, with a companion in-depth review on formal grammar (syntax). Narrative synthesis of 18 studies, weighted by an explicit weight-of-evidence judgement; NO pooled effect size is produced, which is the review's main limitation as a source of magnitude. The corpus is old (searches ran from 1900) and almost entirely North American. Delayed post-tests are nearly absent - only one study reports one.

The synthesis "comes to a clear conclusion: that sentence combining is an effective means of improving the syntactic maturity of students in English between the ages of 5 and 16." Note what the outcome is - syntactic maturity, not composition quality. Differences between studies are in the DEGREE of advance, not its direction. "In the most reliable studies, immediate post-test effects are seen to be positive with some tempering of the effect in delayed post-tests" - i.e. gains are largest immediately after instruction and "tail off somewhat thereafter". In the one study with a delayed post-test, syntactic maturity gains were maintained but less dramatically. The policy conclusion is stated bluntly: "the teaching of formal grammar (and its derivatives) is ineffective; and the teaching of sentence combining is one (of probably a number of) method(s) that is effective." The review also notes that "the emphasis on knowledge about language and language awareness, although useful and interesting in itself, may not be helping students to improve their writing skills."

Low as a threat to direction - the included studies are experimental and quasi-experimental. But the review does not assess selection into treatment across its 18 studies, and its "weight of evidence" judgements are qualitative.