Should an intern who wrote most of a paper and where the first author contributed little request to be first author?
I think you should talk to the PI about the order of authors.  Don't frame the conversation as a demand/plea/request to change the order: phrase it as a question from a very new researcher who put a lot of work into a project and wants to be shown the ropes about why author order is the way it is.  This is not a cover story: I really think that virtually no high school student could know the conventions of author order in the publications in a specific academic field.  So although it is possible that you deserve to be first author or come in some other place, I don't see how you can reasonably know that without gaining a lot more information about the conventions of the field.  

Here is another question to ask your PI: what are the consequences for your career of the author order on the paper?  This is not my neck of the academic woods, but I would guess that a high school student being an author on such a paper is already getting about the maximum amount of credit without being first author.  It may well be the case that the ordering of the other authors has something to do with their academic career...and they may or may not be doing it in what we would agree is a totally ethical way, but unless your contribution was really exceptional, it may in fact turn out to be worse for everyone involved to make a big fuss about it.  

I want to end by saying that academic politics really only matters for academics.  I'm not (at all) saying that you don't have the right to engage in the jockeying for authorship position...but you may have the luxury of not needing to worry about it.  That is a luxury, by the way...