The "switch role to" button is most easily found by clicking on your own name (usually on the top right of the screen) and changing via the last option in the drop down menu there. It is usually not in the admin menu. Also, as the teachers are "non-editting" by your own admission, they will not be able to see the "turn editing on" button. Hope this answered your question.
General help
Switch role not visable for non-editing teacher
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