The strength of this script is definitely your ear for dialogue, particularly the exchanges between the teenage characters, which were authentic and believable. The strength of the dialogue and your characters is what kept me reading to the end.
However, you have relied too much on dialogue to tell your story. You definitely need more action in there, and some visual cues. At the moment your script is just a series of conversations between people, your audience needs something to look at, and any producer needs to be able to gain insight into how your script will be shot.
I liked the premise of your story. It's a scenario that I'm sure is less uncommon than we may realise, and you built up to it quite well. It was an interesting climax to the budding romance between Rebecca and Kyle, which you depicted so tenderly.
I would recommend that you get someone to proofread your script because I spotted a few typos.
Overall, though, you've demonstrated potential and with a bit of work, you could create something that could really resonate with a young audience.
I just read the rest. Good twist, I didn't see it coming. Just a suggestion, but I would be inclined to keep the harry sally thing to a minimum and use the space to develop Kyle and Rebecca's relationship. It's good that they haven't done anything yukki, but the could come pretty close to it. The dad seems to get plonked into the story instead of worked in, if that makes sense. It would've been nice to know how these two felt about their missing father's before he arrived on the scene.