Piagetian Programs

Hattie used ONE meta-analysis for the second highest ranked influence - with d=1.28 (Hattie's Rank=2)

Jordan, V & Brownlee, L., (1981) Meta-analysis of the relationship between Piagetian and school achievement tests. Presented to American Educational Research Association, Los Angeles, CA.

I have not been able to get a full copy of the paper so will have to use other's analysis.

Mike Bell, who runs the Evidence-Based Teacher Network (very pro-Hattie) says :
"the research Hattie cites only refers to the fact that if you assess students using a Piagetian test of thinking level (not on the topic), and then give them a subject/topic test, there is a close correlation. It does not refer to the effectiveness of a Piagetian program."

From docendo:
"I have made a few enquiries and will update this post if I get hold of the full text but it seems quite close to my assumption that it’s about a correlation between tests of Piagetian stages and achievement. I don’t think that’s of any direct use since it doesn’t tell us anything about how we accelerate progression through the stages."

Once again there are significant doubts about the validity of this meta-analysis and therefore the high effect size. It does not appear to measure what Hattie implies it measures.

VERDICT: the quality of evidence Hattie presents for this influence is very poor. I do not believe it is valid to make the claims that Hattie does. So will this advance a child's achievement by 3 years? I very much DOUBT it!