This was tragic and touching. I was pulled in and cared about the characters.
However, there are some issues regarding style and format. I have a few suggestions:
You should put contact information on your title page.
You’re not supposed to number the first page. For some reason that I don’t know, page numbering starts at page two. This suggests that you may have written this with a word processor. If you did, I am impressed because other than the page number, I can’t tell. However, if you use a screen writing software package, things get much easier. There are a few free packages available. I think there is a thread on the message board with some reviews of the free packages. I couldn’t find it but I think I read it
You should avoid using verbs with “ing”. For example, you open with “Oliver is sitting on a school bus, going home, rain pouring down outside, all he is doing is drawing.”
This should be worded more like: Oliver rides home on a school bus. As rain pours outside, he is focused on a picture he draws.
Mia sits in the seat in front of him. She leans around her seat and is impressed by his artwork.
I’m sure my suggestion could be improved on but I think you get the idea.
Another suggestion is to break up your sentences into their individual actions when they are performed by different characters or objects. Also, I would consider making them separate lines as it can make it easier to read. For example, you have, “The bus comes to a stop, the doors opening, Mia looks out the window.”
I would write it as, “After the bus comes to a stop, the doors open.
Mia takes a quick glance out the window."
On your first dialog on page 5, you have the parenthetical (He smiles). Written like that, it should be its own line of action text below the action line, “Mia laughs.”
Also on page 5, you have consecutive dialog entries for Oliver. He says that can’t afford it (being on a plane) and in the next one he asks Mia if she has been on a plane. These should be combined into the same dialog entry. I would only break this into two dialog blocks if something happens between them.
Also on page 5, you have them “feed the ducks their.” ‘Their’ is possessive as in “they rode their bikes.” ‘There’ is a location as in “right there in the park”. Actually, I would leave that little part out. They are in the park. They feed the ducks. They are obviously feeding the ducks that are there (in the park) and not feeding the ducks that are someplace else.
My last suggestion is to proofread your work. I’m pretty sure that you know that I’m (I am ) has a capital I, and your use of a lower case i is a typo.