Every class level has set skills which must be achieved for a child to progress.
Progression depends on many factors; it is important to remember that every child is different and progresses at their own pace.  It is not uncommon for a swimmer to remain in the same class for several terms. All children learn at a different rate. It important to ensure all skills are performed competently before progression to the next level. The more your child pays attention and practices, the quicker you will see results.