The Hampshire Hundreds project was a local authority-led intervention which brought together lead teachers from Hampshire primary schools to provide them with evidence and support for effective teaching strategies to decrease the attainment gap between disadvantaged pupils (aged 9-11) and their peers. The intervention involved a facilitator working with staff from a number of schools, and providing supporting materials comprising the "Hampshire Hundreds Handbook," to provide good quality teaching and support to disadvantaged pupils. The evaluation was set up as a randomised control trial to test the impact of the Hampshire Hundreds intervention in comparison to a 'business as usual' control group, with the local authority leading the training and overseeing the provision of the intervention. As the intervention was run by the local authority it is classified as an efficacy trial. Analysis was completed on an 'intention to treat' basis where schools were compared in the groups to which they were originally randomly assigned. The primary outcome measure was disadvantaged pupils' progress in reading and maths (combined), as measured by InCAS (Interactive Computerised Assessment System) developed by the Centre for Evaluation and Monitoring (CEM) at Durham University. 36 schools took part in the trial. 19 schools were allocated to the intervention group and 17 schools to a wait-list control group, which were offered the intervention at least two terms after the intervention schools. Only 14 treatment schools and 10 control schools completed the post-intervention testing. Key conclusions include: (1) Hampshire Hundreds showed no significant impact on raising attainment for disadvantaged pupils during the evaluation period; (2) Schools were encouraged to respond to the training and support in a way that was most suitable for the context of the school; and (3) This project illustrates that it is difficult to convert research evidence into effective action within schools. It also illustrates the importance of careful piloting of an intervention before attempting an impact evaluation. [The impact evaluation was conducted with Amy Challen and Gill Wyness.]