you chose to buy that lenovo laptop. like i said you can setup a laptop with specs yourself. this is always cheaper and better. even if you buy a premade laptop with installed OS already, you can still check the specs.
well, battery will last longer if your system doesn't use too much, a classmate of mines has a desktop cpu in his laptop(he set it up himself) and it's a really good laptop, but of course, it doesnt have much battery life if its not on power, because it has such powerfull specs. but, there are power outlets in our class so that's no problem. do you need to have to use your laptop on your school when they don't provide outlets? that would be rather weird.
but yeah if you just care about battery life then you could buy a macbook just for that