Gakko ni shiraseru no dake wa yamete kuremasenka.
What does it mean?
Firstable, Gakkouni shiraseru wa
is an incorrect Japanese. You should say Gakkouni shiraseru no wa, or shiraserukoto wa.
Dake means only. The sentence means Only I dont want you to do is to report it to my school.
It implies you can report to the police or else.
On the other hand Gakkouni shiraseru nowa yamete kuremasenka doesnt stress on Gakkou.
Gakko ni shiraseru wa yamete kuremasenka.
Gakko ni shiraseru no dake wa yamete kuremasenka.
What is the difference?
I need contents but basically it means, "Please don't tell the teacher."
gakkoni = to school, to the teachers at school
shiraseru = let them know
dakewa= only, at least
yamete=stop, don't
kuremasenka = please
You can go to Q&A section on italki. Some professional teachers could answer it.