All the first lessons of each KooClass topics are directly available. Each of the remaining lessons can be unlocked using 20 KoKo Credits.
This is designed as a part of the learning process. Your child will benefit more by practicing more questions after learning from each KooClass lesson.
Also, your child can earn the KoKo Credits required to unlock the next lesson easily by doing questions in Mission and Daily Challenge. Together, these form an effective learning cycle.
Find out more on how to earn KoKo credits here.