The following link contains some information and 2 short video clips published by the DfE regarding the 2018 National Curriculum tests for children at the end of Key Stage 1 (Year 2) and Key Stage 2 (Year 6).
5-minute video guide for parents about the National Curriculum tests in Year 6
DfE video guide for parents about the KS1 National Curriculum tests
DfE video guide for parents about the KS2 National Curriculum tests