Watch your grammar. ...Punctuation, spelling, capitalization. Those are the biggies to consider when writing on any poetry/prose site.
If you need help figuring out how to do any of this, there are tons of people here, and I'm sure there'd always be one who'd help you. Myself included.

I really liked your ending; it was VERY funny! You've definitely gotten the spirit of teenagers down pat.
Play around with your "white space," or line arrangement, to emphasize the funny parts and words that hold the most meaning. One key part of this is remembering to always end a line with an important word(i.e., no it, and, but, is, etc.) and try to break it up the way you want it to be read. This means that any places where you want there to be a pause warrents a comma. Longer pauses get a dash or a period, then a line break, or a new stanza.
You have most of the arrangement down... I'm not sure if you tried or not. Just take another look at it and apply some of the above concepts and it'll be much better!

Hope this helps!