Increasing teacher verbal approval has been shown to produce both increased pupil "on-task" behaviour and academic achievement. The present study aimed to address gaps in current knowledge about the effect of different kinds of teacher approval, other than verbal approval, on students' performance. An exploratory study, followed by an experimental study, was conducted with Italian undergraduate psychology students in order to investigate the effect of written approval on their academic performance. The results indicate that, whilst there is some suggestion that students appreciated receiving increased written approval comments on their work, the receipt of such comments was accompanied by poorer academic performance than that of a control group. Possible explanations are presented.