Backstroke can be very tricky and without enough propulsion in the water it can cause children to sink too low in the water with their body.
In order to get the most power in the water and allow for the body's hips to get higher and more level with the water line, kicking is crucial.
However, many children struggle to get the coordination right and the technique with the arms. The arms are very important in controlling the body's streamline position and assist the direction of the power generated from the legs.
TIP: Simply get your child to focus on facing thumbs up when exiting the water and aim the pinkie finger on entry into the water.
A simple exercise is to practice the arm movements standing up in order to get used to the coordination.