Background: "Volume & Heaviness" was one of three Piagetian tests used in the CSMS survey in 1975/76. However unlike psychometric tests showing the Flynn effect--that is with students showing steady improvements year by year requiring tests to be restandardized--it appeared that the performance of Y7 students has recently been getting steadily worse. Aims: A sample of schools sufficiently large and representative was chosen so that the hypothesis of worsening performance could be tested, and estimated quantitatively. Sample: Sixty-nine Y7 school year groups containing pupil data on the "Volume & Heaviness" test and the University of Durham CEM Centre MidYIS test were located giving a sample of 10, 023 students covering the years 2000 to 2003. Method: Regression of the students' school mean on "Volume & Heaviness" on the schools' mean MidYIS 1999 standardized score, and computing the regression at MidYS = 100 allows comparison with that found in 1976. Results: The mean drops in scores from 1976 to 2003 were boys = 1.13 and girls = 0.6 levels. A differential of 0.50 standard deviations in favour of boys in 1976 had completely disappeared by the year 2002. Between 1976 and 2003 the effect-size of the drop in the boys' performance was 1.04 standard deviations, and for girls was 0.55 standard deviations. Conclusion: The idea that children leaving primary school are getting more and more intelligent and competent--whether it is viewed in terms of the Flynn effect, or in terms of government statistics on performance in Key Stage 2 SATS in mathematics and science--is put into question by these findings.