Manek, "как пройти к..." (on feet) "как проехать к..." (in a car) is how we ask for directions. They do sound a bit strange for me (why "through"?). There is a logical connection: "getting through" something emphasizes the surroundings: пройти в дверь. And there is another usage where "про-" refers to distance: прошел километр. прочитал страницу (20 страниц). But still "пройти" sounds for me as walking through something like a door, and not like "turn left, then right, then..." - so I'm surprised that we say it this way. There are many other verbs you can use when askign how to get to somewhere farther than just "turn left then right". Как доехать (до- means reaching a point), как добраться (get to), есть. But you can use проехать as well. As for 'arrive', here the emphasis is on coming. It can be used, if you say "come!" and I ask "how?" but normally you don't use it fordirections.

Generally, the both options are correct, but the latter sounds more naturally. Проехать may also mean “to find a way”, “to drive through” etc. Как лучше приехать к школе? might be translated as “How should I come to the school?”, it’s generally not about the route, whereas the second option is definitely about a proper path.