The top of the Apple iOS store is dominated by apps from Facebook and Google along with the occasional game.
Climbing near the peak of the rankings of late is one service that doesn't fit that mold at all.
Remind, which provides a free secure app for school teachers to communicate with students and parents, soared as high as No. 11 this week on the iPhone as the new school year kicked into gear.
It's currently above Uber, Amazon.com and Netflix.
Not that co-founder and CEO Brett Kopf is surprised. His company has 25 million users, including about 35 percent of primary and secondary school teachers. Last year, the app peaked at No. 3 in the Apple store on Aug. 24, adding 315,000 users per day.
As the 2015-16 school year gets going, Kopf is planning for days with up to 400,000 sign-ups."It's so cyclical that we know to the day, the second, it's going to start and we have to scale up our back end to be able to handle that," said Kopf, whose San Francisco-based company recently moved its infrastructure to Amazon Web Services. "There are these days where it just explodes."
The ascent up the charts was rapid. On Aug. 7, Remind ranked 127th on iOS and a week later had climbed to 92.
Other education apps are also spiking. Google Classroom, an online learning hub launched to the public last year, reached as high as 39 this week from below 1,000 earlier this month, and education social network Edmodo made a similar jump to 50.
On Android, education apps including Remind don't do as well. Remind is currently ranked 84th overall in the Google Play store, even though it's the third most popular in education.
"We are definitely prioritizing Android growth, but we're still seeing a majority of our teachers on iOS," said Kopf.
Backed by Kleiner Perkins Caufield & Byers and legendary partner John Doerr, Remind is doing its best to apply the social media playbook to education. Rather than concerning itself with revenue, the company has raised $59 million, including $40 million in September, to sign up as many people as possible and get members to use the app with frequency.
Kopf, who founded Remind with his brother David in 2009, goes so far as to call it the WhatsApp for education, referring to the texting service that Facebook bought last year for $19 billion. WhatsApp is currently ranked 14th in the Apple store.
But the analogy has its limitations. For one, Kopf says he has no desire to sell the business. And unlike viral social businesses like Facebook, Twitter and Snapchat, Kopf wants to avoid showing ads.
That means he has to eventually find a way to generate revenue in a market that's been notoriously challenging for start-ups. School districts and educators, after all, aren't known for being flush with cash.
Kopf is aware of the hurdles, but he's confident that the business model will surface. Currently, Remind is focused on adding features to the app, which is most popular for letting teachers send secure messages to their class, chat with parents and schedule exams.
Teachers have administrative controls enabling them to set office hours, limiting the time students can message them. Potential future features include handling digital payments for things like field trips and acting as an emergency alert system.
"We feel very strongly that if we build the best communication layer and get to massive scale, there will be lots of opportunities to monetize," Kopf said.
More from Entrepreneur
We created the SYOB course to help you get started on your entrepreneurial journey. You can now sign up for just $99, plus receive a 7-day free trial. Just use promo code SYOB99 to claim your offer.