Why is Scout so looking forward to starting school?

From the text:

I never looked forward more to anything in my life. Hours of wintertime had found me in the treehouse, looking over at the schoolyard, spying on multitudes of children through a two-power telescope Jem had given me, learning their games, following Jem’s red jacket through wriggling circles of blind man’s buff, secretly sharing their misfortunes and minor victories. I longed to join them.