How do I get enterprise enrollment off of my computer

I have a chromebook from school and I have been told by my advisory that its mine i can do as i please with it. So i wanted to wipe the system cause i do not like people being able to get into my system easy nor do i like being spyed on. I have tryed the whole thing about unhook the battery and re img stuff and no dice. i have removed the writer screw and everything a still no luck how can i beat this who has a answer for me on this. Should i buy a new harddrive or would that help at all. I can not even make it to the developer mode its locked. please help