Teacher Rob Tarrou is helping students around the world with math, without leaving St. Petersburg, Fla, the Huffington Post reports. Tarrou has been teaching at St. Petersburg High School for 17 years, but started posting video lessons to YouTube last fall. Now, “Tarrou’s Chalk Talk” [1] has more than 300 videos covering subjects from factoring to matrices, and has more than 3,000 subscribers from more than 100 countries. With more than a half million views, students in Australia, Sweden, India and Brazil, among others, have all written in to express their thanks and support. Comments on the “Tarrou’s Chalk Talk” Facebook page sing the educator’s praises [2]. The videos started as a way for Tarrou to teach a student who couldn’t attend class [3], the Tampa Bay Times reports. Now, his St. Petersburg High students use them to supplement their learning, share with others, and wish their other teachers offered the same out-of-class resources…