How to make all participants and their live camera visible to all participants of a meeting?

For our home schooling during Covid19 times, we as an elementary school started leveraging Jitsi meet. We are currently experiencing the effect that the camera content of 4 participants only will be shown, all other participants are displayed in the grid with plates just showing their initials, but not their live camera pictures. What are we doing wrong? Is there any idea how to make all participants’ camera picture (up to max 14 people) visible? Thanks