Ключевые слова: background, billboard, black, blackboard, blank, board, chalk, chalkboard, childhood, class, classroom, college, communication, copy, dirty, education, elementary, empty, erase, eraser, exam, green, grunge, knowledge, learn, lecture, lesson, material, old, primary, remember, reminder, school, scratch, space, sponge, study, teach, teacher, test, texture, used, white, write,