hey, I'm also 16 years old also so I feel like i can kind of relate to your situation. I started feeling extremely stressed about school and considered very seriously about dropping out, but then I realized maybe it's not really even school that is bothering me. I realized that I just was not happy within myself. And it will probably be hard to tell your parents how you're feeling because you might feel like you're letting them down in some way, but it's not your fault AT ALL, being a sad or a little depressed is completely out of your control. By telling your parents about it is being really strong because that means you realize that you're not yourself and you want to get help and honestly it will only get better from there because then you may or may not get some medicine which can do wonders. and will put you in the right frame of mind to get your life back in order. but also if you feel like your class load is way too much you should go talk to your school counselor about it because they can really be of a lot of help. I was taken out of one of my stressful classes and was re- scheduled so that I could have a study hall in place of it while I'm trying to get myself in a better place.

It took me a while to realize that I was unhappy but now that i've accepted it, i can forgive myself, and start working on getting to a happier place, because everyone deserves to be happy, never blame yourself for your unhappiness and try not to be afraid of letting your parents know because you're not alone. and by ignoring it you leave it there to grow into something bigger. you've got to learn how to fall before you learn to fly.  hope this helped  , best of luck.