Turning off chat function is not working

Hi,

I am a primary school teacher running ZOOMS for remote learning. 

Recently myself and my colleagues have noticed that we are unable to turn off chat during a ZOOM, which can be frustrating with dozens of nine year olds.

We have tried the below methods but it does not seem to stick and immediately reverts:

1. Click the Security button and untick the Chat option

2. Open the separate Chat window and click the three-dot menu. This allows you more granular control over who the participants can chat to.

Help would be greatly appreciated.