Out with the school, in with the monsters..

Hey peoples,

When i started practicing for lucid dreaming after a while i realised that i was having alot of school dreams mostly primary school.I have had 2 lucid dreams after just over a month of practicing, and now ive been realising that i dont dream of school that much anymore, but now its monsters or dreams with zombies after me. lol. Its like my school dreams have been replaced, i have 3-4 dreams a night and one of them always was school. Does anyone know this?and why?