Hi Erwin,
You've probably noticed that there is not a single 'Turn editing on' capability. The button is displayed if necessary for other things, such as moving course
sections.
Depending upon exactly what you want your non-editing teacher to be able to do, I suggest you edit the role and browse the list of capabilities, allowing whatever you find necessary.
Alternatively, you may find it easier to create a copy of the teacher role and remove unwanted capabilities. Please see the documentation
Creating custom roles for further details.