Ключевые слова: background, blackboard, board, boy, chalk, chalkboard, child, class, classroom, cleaning, clever, closeup, color, concept, copy, development, education, elementary, girl, green, growth, hand, junior, kid, learning, lesson, lifestyle, little, math, mathematics, number, person, primary, pupil, school, schoolboy, schoolgirl, semester, smart, space, sponge, student, study, studying, sums, task, teacher, text, texture, wiping,