How can I get ideas for an online community for students?

As far as targeting a single high school, I don't know. But, in terms of platforms this audience uses, Tumbler, Instagram, Snap Chat & Vine would be good targets.

I would invest in Instagram advertising. Your target market uses Instagram heavily, so this will be an effective use of advertising dollars. Any kind of social media advertising will get you exposure with these age groups. You might set up a twitter account if you haven't already. You can promote your tweets and get your site out there. Maybe offer some kind of promotion for retweets, or special service or discounts through tweets that only your followers get or are eligible for. If you want an example- @HiddenCash on twitter. Hidden cash gains followers by tweeting out clues to where the cash is hidden in various locations. Best of luck to you!

We've used MeetingBurner with success for our webinars. The price point for a large audience is not too high. It also has recording and automated webinar capabilities.

Investors do not fund ideas. You must prove significant market interest in a product. Statistics that highlight potential don't translate into your product's revenue. Investors want to see how they will get a return on their investment. As for a business plan, be mindful that this is an investment document that in addition to a narrative must contain solid CPA-driven financials. Investors also want to see that you have put more than thought into a start-up before they invest. Need a way forward? I'm happy to assist.

Qualifications on the answer: Created the first website to be ever commercially licensed by a ministry of education for in-school use (Brainium 1996). Was a VC associate at a 500,000,000 firm called Knowledge Universe focused on all things education-related that intersected with technology. Short Answer: Yes and no. Longer Answer: Learning analytics is one of those "lightening in a bottle" kind of industries. Everyone knows it's going to happen, whomever makes it happen at scale first, will have a huge advantage, and even more niche plays in this space will still create massive value for shareholders and significant transformation of education as we know it. That's the good news. The problem is that funding startups in the education space that are dependent on "permission" being granted by existing institutions and their employees is very much hit or miss. It's getting easier to raise a $500-800k seed round for a good idea with a good team, but the problem is that getting the next bigger round is very challenging in that the models of most of these seed-funded companies are not growing fast enough to prove to institutional investors that a growth model of the idea being very big in a relatively short time-period is credible. So if you're intent on pursuing this, I'd be sure to focus entirely on how you can get growth and adoption with requiring little to no institutional buy-in which sounds almost impossible on the surface of the area you're exploring but I believe isn't actually impossible. I'm very passionate about this space and want something like what you're describing to succeed so would be happy to do a quick call to hear where you're at and see if I can provide you some actionable ideas on how to reduce the friction / improve adoption of your analytics product.