New Delhi, Feb. 14 -- Last July, Zahir Mirza sent his pre-teen, Ayaan, to Sahyadri School in Maharashtra, where access to phones is limited and students are encouraged to write letters. Mirza, a professor of visual communication and design thinking at Sir JJ School of Arts in Mumbai, started sending illustrated letters to his son. The topics range from reminiscences about their holidays, educational subjects with water-coloured drawings, explaining phrases like rabbit hole and recounting cricket matches with detailed portraits of players. Even the envelope has a small illustration. According to Mirza, "It makes the postman happy." As one would imagine, these letters are a rage with his son's friends too. Ayaan responds to the letters with...