Ok, we're one step ahead, you decided you want to go through with it...

Do you think you'll change jobs, if you join the family business now, once you've finished your school?

If not, why would you delay your career?

But I should mention... Andres makes a damn good point, this is one of the last few years you have complete freedom (though it may not seem like you do), you can save money for a long journey abroad, enjoy more time with friends, expand on other skills... If this however does nothing for ye: the sooner you start your job, the sooner you'll grow into it and climb the ladder...