What exactly is it that causes a video to go viral? What makes a certain post blow up Facebook, break the Internet or overwhelm YouTube?

Well, cute kids are a certainly a good start. So are the heroes who inspire us, those who fight against all odds to succeed in life or those who succeed in sports by winning a National Championship.

We had all of that in some of our most-watched CMSD-TV videos on our YouTube channel, in raw video posted directly to Facebook or even on Twitter or the live-streaming service Periscope.

You also showed up in large numbers this past year to watch videos of our scholars show off budding leadership skills, their mad chess skills or even good nutrition habits.

Oh, and there was dancing – lots of dancing, from CEO Eric Gordon’s fabulous “At10Dance” that jump-started our “Get2School. You Can Make It” attendance campaign to the breathtaking moves from our Cleveland School of the Arts students to a Collinwood High School principal busting a move to inspire her students.

So in case you missed it, here are some of our most popular videos from 2015, starting with the video at the top. The Dec. 10 video itself is less than a minute long and described in one simple sentence: Nathan Hale kindergarten students get into sight words with teacher Maryanne Nesbett.

It shows the students, all wearing laminated vests with oversized letters of the alphabet, sight spelling the word “gum.”

Simple, right? People went crazy for it: The video has been viewed more than 36,000 times, has reached more than 200 people on Facebook and has been shared nearly 500 times, including by many group pages interested in teaching techniques. It even drew 64 comments, from simple admiration (“Awesome!” “Adorable.”) to the more practical (“I’ve never seen letter vests! I have to get these.”)

Below are nine more of our most popular videos, ranked in no particular order. To see all of our CMSD-TV work, go to our YouTube page or check us out on Facebook, Twitter,  or Instagram.   

• Amanda Berry and Gina DeJesus receive honorary diplomas. The two, kidnapped off the streets of Cleveland during their school-age years, received honorary diplomas at John Marshall High School’s commencement on Wednesday, May 27.  The two women, along with Michelle Knight, escaped in May 2013 from Ariel Castro’s home on the city’s near West Side. It has been a story that continues to grab national attention. Amanda was a student at John Marshall when Castro abducted her on April 21, 2003, the day before she turned 17. Gina, then 14, was taken as she walked home from Wilbur Wright School on April 2, 2004. She would have gone to John Marshall.

• Cardale Jones announces his return to OSU during press conference at Ginn Academy   The Glenville High grad stunned the sports world in early January by announcing he would return to Ohio State after winning a National Championship  -- and he chose to come back to CMSD to make the national announcement. The CMSD-TV video had more than 11,000 views. A separate video showing CMSD reaction had another 2,000-plus hits.
• "We Are CSA," our Cleveland School of the Arts video, presented at the grand opening of the school in October. CSA joined Max Hayes and John Marshall as the three new high school buildings to open this school year. 
• Which brings us to dancing videos. Take it away, Eric "Hitch" Gordon: The CEO's "At10Dance" video drew more than 3,300 hits on YouTube and thousands more on Facebook. The light-hearted video spurred dozens more from students, teachers, principals and community members -- all in support of the "Get2School. You Can Make It!" campaign, which has hit its goal for each of the first two grading periods. 
CMSD scholars at Clark Elementary got a visit today from the Harlem Globetrotters. John "Hawk" Thomas entertained with...

Posted by Cleveland Metropolitan School District on Thursday, November 5, 2015

• And then there's Collinwood High School Principal Maria Carlson. Her own dance video, taken in bits with Railroader students and staff, had nearly 1500 hits on YouTube.
• CEO Gordon also drew a big crowd with an annual discussion of why and when the District closes for snow (calamity) days.
• You also loved watching a video of a January ceremony to rename East 112th Street "Steve Harvey Way" in honor of the Emmy-award winning television host and CMSD graduate.
• A short November Facebook post (right) about a member of the Harlem Globetrotters visiting Clark School to talk about an anti-bullying campaign also hit big, reaching more than 74,000 people. 
• More than 1,000 people also watched the Facebook video that accompanied a CMSD News Bureau story about students at Max Hayes who impressed Leadership Cleveland visitors this fall.