The effects of praise on student on-task behaviour, academic self-concept and numeracy enjoyment were investigated. Four year four classes and their teachers participated. Two teachers were instructed to use specific praise and two to use positive praise. Classes were independently observed on four occasions, twice before and twice after the praise intervention. Student on-task behaviour, numeracy enjoyment and academic self-concept were measured and teachers' use of praise was observed. Specific praise promoted more on-task behaviour than positive praise and significantly increased academic self-concept. Ratings of numeracy enjoyment were not significantly affected. Implications of this research for teaching practice are discussed.