Students solve problems in Crystal Kirch's pre-calculus class at Segerstrom High School in Santa Ana, Calif., Wednesday, Jan. 16, 2013. A growing number of teachers are implementing what is known as ... more

Students solve problems in Crystal Kirch's pre-calculus class at Segerstrom High School in Santa Ana, Calif., Wednesday, Jan. 16, 2013. A growing number of teachers are implementing what is known as "flipped learning," in which students learn lessons as homework, mostly through online videos produced by teachers, and use classroom time to practice what they learned. (AP Photo/Jae C. Hong) less

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Associated Press | Photo By Jae C. Hong

Sun, Jan 27, 2013 6:40 PM EST