I'm a computer programmer in high school without any job experience. What can I do to be able to get an internship at a tech company?

There's a few things you can do:

Do programming projects at home. Put them up on a website for the community to see and use / give feedback on. You might even be able to make some money this way! Employers love this - it shows you love programming and have an interest in it outside work / college.
Take part in the programming community. Keep up to date on the latest technology so you can talk about it in interviews. For example with PHP you might want to keep up to date on various frameworks like Zend or jQuery. Twitter is great for this.
Talk with companies and say you want the experience. You might be able to get a short term contract (with no pay), but it's something to put on your CV and you'll learn a lot! The employer likes it because it's free work for them, and gives them a chance to see you working to see if you will fit in with the company. If you do, they might even offer you a job at the end of the temp contract.
Go to conferences/meets. They are sometimes free and gives you a great chance to network with people already in the industry.

Hi Anina,
I know its tough to find internships while you are still in high school, however, there are spots out there. Make sure you get the word out to your friends, your parents friends, teachers and anybody else you can think of that you are looking for a chance to build your experience. It is often personal connections who can open doors and get round the "college only" problem. Definitely consider volunteering and look out for hackathon's that may be taking place in your area.

All the best,
Jim

Hi Anina,

It depends on what your sibling is looking for in the internship. If they are looking experience, then I would look at volunteer organizations, who are always looking for help to optimize and help them keep their systems/programs running. if they are looking for salary, then that will be much harder as they will then have to compete against applicants from college.

Given that your younger sibling does not have any programming work experience, I would recommend that they complete Introduction to Computer Science and take AP Computer Science. If they score well in the AP exam, that will count as "college course work" and give their resume a boost. In addition, they should build project portfolios (from their AP class) that they can show their perspective employer.

But like everything in life, it will depend on perseverance (keep looking) and luck - be ready when opportunity knocks.

All the best.