recently created new applie id but i cannot remove my old icloud email address from my ipad to update with my new one

my original apple id used my school email address. I wanted to switch that over so i created a new apple id and added it to my phone no problem but when i tried to add it to my ipad it asks me to sign into my old apple id in order to update or erase it. but i cannot sign into it as it no longer exists, even when i try the iforgot.apple.com to reset the password it states no such apple id exists. how do i delete the old id from my ipad and update with the new one?