Kids don’t try their hardest unless they think someone’s watching. Overcrowded classrooms and distracted parents can make pouring effort into school work feel pointless. But Seesaw‘s app turns their assignments into social media they share with teachers, peers and mom and dad. Now it’s invading schools across the country and just raised a Series A round from LinkedIn CEO Jeff Weiner and others.

On Seesaw, instead of racking up likes or receiving comments on a selfie, students get positive reinforcement on their quizzes, drawings and science projects. And for instructors, Seesaw serves as extra eyes, allowing them to focus on managing the classroom, then later watch self-recorded videos of students completing a task or working through a question.

By getting kids to care about classwork and giving teachers a closer look at their students’ process not just output, Seesaw has quietly become one of the most popular learning tools for elementary school students. Now half of all U.S. schools have teachers using Seesaw, up from one-quarter in June 2016 when we profiled the education startup. Millions of students now use Seesaw each month in 150 countries. And the startup has 1,000 schools and districts paying for the premium version of Seesaw.

“Most elementary school products are dumbed-down versions of high school products,” says co-founder Carl Sjogreen. Seesaw’s design relies on big, obvious buttons and the familiar camera feature most kids are already used to playing with. This makes creative projects easier to assign and more rewarding thanks to digital show-and-tell. Kids don’t feel like their assignments just end up in the trash once hastily graded. “Much of the traditional classroom is about getting kids to express themselves through a worksheet. Can you think of a more constraining way to create than fill in the blank on a worksheet?”

Seesaw was co-founded by Adrian Graham and Sjogreen, a former Facebook director of product management who had sold it his travel startup NextStop. He launched a social app called Shadow Puppet in 2013 as a way to record voice-over for photo slideshows. This was a cool idea back before Snapchat Stories had even launched, and it raised money from Greylock’s Discover fund.

While Shadow Puppet flopped with consumers, some teachers and students loved using it for showing off class projects. Nine months in, he pivoted Shadow Puppet and Seesaw launched in 2015. Now it’s picking up steam with its Series A of an undisclosed size from investors, including LinkedIn’s CEO, former DFJ partner Bubba Murarka and Wayee Chu of Reach Capital. Some of that cash went to hiring Mike Wu, former CTO of Instagram competitor VSCO, as Seesaw’s VP of engineering.

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