Ключевые слова: 1, back, background, blackboard, chalk, chalkboard, child, class, classroom, cleaning, college, color, copy, dirty, draw, education, exercise, green, homework, kid, knowledge, learn, lesson, nobody, note, object, piece, pieces, pupil, school, september, space, sponge, stains, streaks, study, table, task, teach, teacher, text, university, white, wipe, wooden, write,