The Foundation Phase (introduced in 2008) provides a developmentally appropriate experiential curriculum for children aged 3-7 in Wales. The Welsh Government commissioned independent evaluation (led by WISERD) aims to evaluate how well it is being implemented, what impact it has had, and ways in which it can be improved. The three-year evaluation utilises a range of mixed methods at a national and local scale. This is one of four papers focused on impact. It draws on 239 classroom/setting observations, 357 practitioner interviews, 604 school/setting and 671 Year 2 survey responses, seven Year 2 focus groups, and 37 Local Authority and four non-maintained organisation interviews. (author abstract)