Thirty-six TESL trainees of three different age groups used classroom theory and practical experience to shape their own knowledge of English grammar. Participants completed a series of three grammatical explanation tasks over the course of two academic terms. Analysis of results revealed that the two groups of older trainees (23-34 years and 35-62 years) were able to make significantly better use of classroom instruction than their younger counterparts (19-22 years). (Author/VWL)