Each school can set which entries can be created and viewed by which user group.
In order for the teachers to be able to generally create and view entries, you first need the "View class register" authorization. You can activate this for individual users in the profile via the user administration or for all teachers in the admin area under "User roles".
You can then further adjust the authorization in the admin area under "Visibilities & rights".
The standard settings for teachers with the "View class register" authorization are as follows: