How exactly does ED work?

<p>I want to apply to Columbia on early decision, but a good chunk of my academics will be in my senior year. If I apply for early decision at the beginning on my twelfth grade year, will my extracurriculars and classes be noted? Or is part of ED that your junior year is supposed to be really solid independent of senior year?</p>

<p>If someone could give a quick comparison I’d really appreciate it.</p>

<p>My apologies, when I said comparison I meant vs regular.</p>