The shock hits at the end of 7th grade — that’s when city students get handed a humongous book with detailed descriptions of more than 400 NYC public high schools.

Suddenly, adolescents must think about their future — out of any high school in the city, which is the right one for them?

It’s confusing, intimidating and frustrating. Blow it off, and you could get stuck in a dead-end high that won’t prepare you for college or career. Invest the time and effort, and you may get a first-rate education.

Understanding the twists and turns of the system is key to snagging a seat in the best school for you. Here’s some crucial advice: