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.