What punishment should a 13 year old get if he murder a cop in school?

[Franzl]

Is he killing the cop in self defense...an accident?  You said "kill" not "murder", but your options make it seem like you meant "murder".... so it's a little confusing.

This 13 year is murdering the cop in self defense for what a cop did to him on the weekend. Some town cop was out on the streets and suddenly talks over with this 13 year with why the kid was walking on the streets at 11:30 at night in his small city. Then the 13 year old talks trash and the cop suddenly goes Rodney King on the kid. This marks the revenge for the 13 year old. On that Monday, two days later after the cop brutality treatment of the 13 year old, the 13 year old swiftly stabs a cop right in the stomach four minutes before school started. The cop dies afterwards and the 13 year old is arrested for assaulted murder of a police officer.

He would get about 5 to 10 years in Austria.

He wouldn't get any criminal punishment in Germany. Strafmündigkeit begins at age 14.

[Franzl]

So, huh, you can do anything you want if you're 13 and under?  I hope you at least miss a week of school if you murder a dozen of your classmates.

No. They can certainly lock up the child for psychological treatment and such (for several years), but it's important to distinguish between punitive sentences and others in German law (and I imagine Austrian law as well).