I still don't get the whole cat joke that the school boys pulled on their teacher.  I don't see how the audience didn't see the boys lowering the cat, but whatever.  Tom looked at that prank as the start of fun summer vacation.  Tom joined what's called the new order of Cadets of Temperance.  The book doesn't describe what this group thing is at all.  It just says how the rules of being a part of this was that there was no drinking or swearing aloud.  Tom had a hard time with this because he was used to swearing and drinking since he supposedly does it all the time.  But then finally, Tom couldn't take it anymore, so he pulled out of the group.  But then he no longer had any desire to do those things since it wasn't against the rules anymore.  Then it goes on to talk about how Tom's summer was really boring and a big dissapointment.  Then he ended up getting the measles, and was bed ridden for two or three weeks.  He got better and started to go to some of his friends' parties but he was still having a lame summer.  Another thing that had added to it was that his true love/enemy was out of town for the summer.  He then goes through a weird phase where thinks that he will not be saved when he dies because he is a really bad sinner.  He sees how all of his friends are being righteous by either doing service or reading scriptures.  Even his "wicked" friend, Huckleberry Finn was quoting scripture.