When these competencies were combined during tests, for example, then I experienced difficulties.

 

When I understood competence A at one time I understood, competence B also understood, competence C also understood, but when these competencies were combined during tests, for example, then I experienced difficulties.

Answer:

A younger sibling's understanding of these competencies can be said to be less meaningful (meaningfulness), this can be seen when these competencies are combined, then the younger siblings experience significant difficulties.

The solution is simple, try to link competencies A, B, and C in a schema / chart. So that the younger siblings will get a flow on the competencies that are learned.