They work as private tutors and soccer coaches, as waiters, grocery clerks and ride-share drivers. Across the country, 18 percent of teachers earn income outside the classroom, according to a National Center for Education Statistics report released Wednesday. The finding comes from a nationally representative survey of teachers conducted in the 2015-16 school year. The report emerges in a year when teachers in West Virginia, Oklahoma and Arizona have protested, calling for higher wages and for states to increase school funding.