The assessments were introduced following the introduction of a National Curriculum to schools in England and Wales under the Education Reform Act 1988. As the curriculum was gradually rolled out from 1989, statutory assessments were introduced between 1991 and 1995, with those in Key Stage 1 first, following by Key Stages 2 and 3 respectively as each cohort completed a full key stage. The assessments were introduced only for the core subjects of English, Mathematics and Science. The first assessments in Key Stage 1 were a range of cross-curricular tasks to be delivered in the classroom, known as standardised assessment tasks - hence the common acronym 'SATs'. However, the complexity of the use of these meant they were quickly replaced by more formal tasks. The assessments in Key Stages 2 and 3 were developed using more traditional tests.