Throughout much of the twentieth century, Sunday schools in Britain played a significant role, both disseminating and forming Christian faith. There was near universal attendance at the schools, and as a result there was widespread exposure to Christian teaching and hymnody. Despite this, their role as an educational arm of the churches is under-researched. This article considers the experience of the schools from the beginning of the century until the outbreak of the Second World War. It examines how and what Sunday schools taught during this time, and the extent to which they adopted pedagogical developments. The article also considers the responses of the schools to the various education acts passed in this period. In addition, it examines what the schools themselves, their scholars and the churches thought of their effectiveness, and reflects upon the tensions that arose between the schools and the churches. The article concludes that Sunday schools were an integral part of the churches’ educational reach in society and therefore deserve much more thorough examination by historians.