ABSTRACT
The crucial question for any educational intervention should be: is it effective? or does it work? In research terms the only reliable way of assessing effectiveness is through the use of a randomized controlled trial (RCT). Because the focus of this review was on ‘effectiveness’, studies using rigorous study designs to assess effectiveness were required: this implies the identification of relevant randomized controlled trials (RCTs). The RCT is an experimental design that provides a way of reducing the risk of selection biases at entry to a study. Selection bias is where children are ‘selected’ into a group in such a way that this affects their educational outcome. Because children have been selected into a group (either by their teachers, parents or themselves) they are likely to have different characteristics from children who have been selected into another group. To avoid biases associated with this selection it is imperative to use the RCT method.
