In the United Kingdom tensions have existed for many years between the pedagogical traditions of pre-school, which tend to adopt developmentally oriented practices, and the more formal or subject-oriented curriculum framework of primary school. These tensions have been particularly acute in the context of Northern Ireland, which has the earliest school starting age throughout Europe. In response to international research evidence and practice, a play-based and developmentally appropriate curriculum, known as the Enriched Curriculum (EC), was introduced as a pilot in Year 1 and 2 classes in over 100 primary schools in Northern Ireland between 2000 and 2002 and continued until the Foundation Stage became statutory for all primary schools in 2007. This paper outlines four key lessons that have been learned from the first four years of the evaluation of this experience. These include the value and the meaning of a play-based curriculum; the importance of teachers’ confidence and knowledge; teaching reading in a play-based curriculum; and easing transitions in a play-based curriculum.