Your child’s progress will be reviewed when they’re between 2 and 3 by an early years practitioner or health visitor.
Their class teacher will assess them at the end of the school year when they turn 5.
The assessment is based on classroom observation - your child won’t be tested. It uses the early learning goals, which can be found in the early years framework.
You can find out more information about the assessments here: https://www.gov.uk/early-years-foundation-stage