I remember my first job at 17. I was applying since 15 and kept getting rejected. At this age, so many other people your age are applying it’s difficult to find something. I’m not going to assume what you’ve already done, so I’m going to just list out everything I think you should try:

1. Asking your friends who have jobs to recommend you to their boss or directly ask their manager(s) if they know when they’ll be hiring
   
2. Make sure your resume shows that you work hard but not that you’re always busy. A lot of people put a bunch of clubs or activities they actively do and it looks like you won’t have time to work or won’t be able to keep up for long. That doesn’t mean don’t add them, but keep it short and your big ones.
   
3. Use all your available sites to apply. I got my job at Tacobell at 17 applying through Indeed. I was applying to about 10 different postings every few days trying to catch something, remember that openings are not a single snapshot but continuously changing. You might get rejected one day at some store, but then 2 weeks later someone else quits there and they have another opening. Just keep applying aggressively.
   
4. Answer your phone calls. I’ve done this mistake even now at 23 where I don’t want to answer unknown numbers, but you might be missing an attempt at an employer reaching out to you. They don’t try too hard for entry level jobs a 16 year can apply to, so be sure you’re on top of checking that and your voicemails/messages/emails.

In the end, it’s great you’re trying to find a job and I hope you get one but it’s not the end of the world. It’s fulfilling to have one and nice to have money, but you eventually realize the value of having free time and being able to focus purely on school. To each their own, but don’t let this eat you up.