Lenovo tab m10 plus 3rd gen

I’m sorry if I make some mistakes, english isnt my first language.

My school gave its students a lenovo tab m10 plus 3rd gen and since I’ve left high school I’ve been trying to delete all school related things but I can’t ??? I’m not sure how to explain it but when I turn it on it has my schools name on the screen, they still have access to my history and I can’t access some websites because of that I don’t know what to do. I tried rebooting it twice and it doesnt work please help me