Laptop needed for student Campaign

I'm a grade 12 student needing a laptop for my computer science subject. I've used my mother's old laptop, a Lenovo IdeaPad, for grade 10 and 11, but it's slow and doesn't work unless it's plugged in, which means I can't use it at school. It keeps freezing and crashing, so I often lose my school projects that I've been working on. I'm planning on saving the money to buy a laptop that works well to use for grade 12 and college. The money that is left, I'll save for college. Any amount would be greatly appreciated.