What is an appropriate discipline for 8 year old?

Tweet

Today when I went to pick my DS up from school, I had to sign a sheet that informed me of a negative behaviour that he was caught doing. They have switched schools and it is only 4 weeks in. We have never had this type of problem with him before. I feel it is my duty as a parent to make sure that they are held accountable and that we are working with the teachers to resolve any type of conflict that there might be. When I asked him he told me the same story that the teacher told me and admitted he knew it was wrong. He seemed sort of remorseful at the beginning then was kind of cold about the whole thing later, when my DH came home. Upon his suggestion (my DS), we have taken away any media (video games, computer, TV) for 1 week, and also he had to go to bed right after dinner. We have made it our expectation that he go to the school tomorrow and apologize and ask for forgiveness. I had him write a letter of apology but because he filled out a 'accountability letter' for me to sign I felt it might be a bit over the top. We had a 'discussion' or more like lecture on what reputation and character mean, and that what it means to tarnish those. Because something like this has never really happened before I feel maybe we might have been a bit harsh, but on the same token we wanted this to be a big impression on him so that he knows it is a big deal. Do you think we are being to harsh on him or should we be doing more, any comments would be appreciated.