How can I get in touch with decision makers at Chinese education startups?

Domain expertise and talking to users. By working with the users you want to sell to or even just the industry, you will see how they do things - and more importantly, see what it takes to influence their behavior. You may realize pain points you didn't see in the first place - and may even end up rethinking your parameters/format of downloadable as well. It's a huge commitment, however, so most people do the second, which is talking to users. Read Paul Graham's essay on launching. Startups are a marathon, not a catapult. You are looking for consistent, incremental progress and growth over the lifetime of the company, not one short-term rocket-ship blastoff.

Where? The world is a big place. Short answer, conferences are not that useful unless you are on a panel/speaking etc. Recommend you focus on building grass roots. Conferences can be a part of it, but how you do conferences matters, otherwise is an expensive use of cash.

Others have addressed social media here. Sure, that is important, but is only one piece of the puzzle. A comprehensive --- and tested --- marketing plan is the key. As a former CMO for an international higher education student-centric nonprofit that depended on direct/integrated marketing for 80% of its success, I suggest that looking at any and all channels is imperative. If you do not have a quality direct marketing list, then going to where potential students --- and their parents --- are going will be the biggest key. On the web, that will be the most-visited relevant sites that enable you retarget via companies like AdRoll. The other concern is the ever-expanding use of ad blockers. Therefore, simply "advertising" is not as powerful as it once was. Becoming a resource that will draw people to your site and blog will naturally increase your exposure via Google and other search engines over time. This is just a cursory overview, since I do not know your exact product and business plan. Feel free to reach out if you'd like to further discuss your challenges.

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.

There are a lot of things to keep in mind that would make this answer REALLY long. But, one of the most important is simply to remember your audience. As educators, we tend to get caught up in scholarly jargon and forget the simplicity that we need to reach our audience sometimes. Also, be specific to which level of audience you are targeting. Elementary? Secondary? Higher Ed? And lastly, don't overanalyze. Create a plan, then GO! Course correct on the way!