400 lashes and don't be gentle!

I can't believe what happened today. I'm experimenting with puni...I mean deterrents of a different sort these days. To be specific, I'm trying not to use up all of my free time after school and I refuse to give up my lunch for detentions. I'm trying writing assignments in which the students are reminded of the silliness of their behavior while enduring some mindless tedium - writing sentences. I gave some to a student because he would not stop talking. I had to have given at least 10 warnings until I assigned 20 sentences. He didn't stop. I changed it to 25. He didn't stop. I changed it to 30. He just didn't get it and the next thing I know, he's up to 400. That is not a typo. I actually assigned 400 sentences. It's worse though, I gave him about three sentences that have to be written 400 times. I am absolutely in shock. 400 sentences...unbelievable.