This is what I have listed on my resume so far:
contact information:
- address
- cell phone number
- email
volunteering experience:
- organization
- location
- role
- time frame
- description of role
school
- name of school
- location of school
- grade level
- unweighted and weighted GPA
- AP courses that I have taken and am currently taking (along with my score for AP courses that I have currently taken)
extracurriculars
- name of each club
- description of what i do in each club and my involvement in them
accomplishments
- accomplishment
- date
- mini-description of needed (for example, I had to say that I advanced to state after placing 2nd at regionals for math team)
languages
- english and chinese (not really much to say here)
Is this enough? Or should I mention skills too, like being a good communicator, a team player, hard worker, flexible, etc?
Is there anything else that I should be including? I’m a bit worried for applying for this internship because it’s probably really competitive, but it’s the perfect internship because it combines the two things that I want to do with my life: business and STEM. It’s also conveniently close to home compared to the majority of other internships being at least 40 min. away.
Any help will be great! 
I would not put stuff like “team player” – the goal is to show that through your experiences, not tell them flat-out.
Okay, thanks @bodangles, so should I not include skills then?
If you have hard skills, like programming languages, experience with Microsoft Office, etc, list those. Soft skills are subjective – personally, I dismiss them if I see them on a resume.
I’d wouldn’t try to overstate your qualifications. For example, do they care what APs you are taking? Only if they are relevant to the position. Similar with ECs for the most part.
I’d use give you weighted GPA (but say so).
That’s a good point @intparent, I definitely will be taking out my AP classes. Thanks for the advice I think I’ll keep most of my ECs though. The job is about business and STEM and in the application they emphasized the importance of leadership and communication, and all of my ECs fall under that (besides a few speech contests that I won several years ago).
What do you mean by “overstate your qualifications”?
I just mean that puffing up the length of the resume with things not relevant to the job won’t help you.
Is this an internship commonly filled by HS students, or are you competing against college students?
Oh okay, I wasn’t doing that.
This is an internship for high school students only @intparent.
Good, then your chances are better.