If teacher punishing student is also supposed bad karma?
Buddha did not do any violence. The suttas say:


  it is true, Kesi, that it's not proper for a Tathagata to take life. But if a tamable person doesn't submit either to a mild training or to a harsh training or to a mild &amp; harsh training, then the Tathagata doesn't regard him as being worth speaking to or admonishing.