Ключевые слова: back, background, banner, billboard, blackboard, blank, board, business, chalk, chalkboard, class, classroom, concept, copy, design, dirty, education, empty, flat, frame, gold, golden, graphic, icon, illustration, isolated, learning, lesson, object, old, red, retro, rub, school, shadow, sign, space, study, teacher, template, university, white, wood, wooden, write,