Thanks for your question. My biggest suggestion with something like this is to have active Social Media. The majority of Highschool kids have Instagram, Facebook, Snapchat, and more!
My recommendation would be to have creative images and cool captions/hashtags to gain more followers and more interest in your website first before spending the money on media coverage or getting investors. The more followers you have on social media from highschoolers, the more people will talk about your site at school and the more engagement and traffic you will get to your website.
I would also recommend having a Facebook Page where you can consistently post as well. You can link this to your Instagram account and have similar posts going on both platforms.
I really would recommend Facebook/Instagram Advertising. This is extremely budget-friendly and would definitely attract a number of high schoolers. Using creative images and intriguing captions to draw in people to your site is key. For example, you could do, Ever wondered if your Highschool crush likes you? Well, now you can check for Free with Zuli. Use emojis to make the person more interested such as hearts or a person emoji.
I myself am 21yrs old and so I have a rough idea of what people similar ages/younger than me are interested in and what would draw them in. I run E-Commerce Businesses where majority of my products are selling to teenagers. I also have social media that I run for my businesses and run Facebook/Instagram Advertising. I feel this project is something I could help with if you ever needed someone. Any questions, don’t hesitate to contact me firstname.lastname@example.org