Venkatadri Express

Ram Murthy is a retired headmaster who does not tolerate mistakes and threatens to banish any family member who makes more than a 100 mistakes. His youngest son Sundeep, who has racked up a score of 99, gets separated from his family when he misses the Venkatadri Express to Tirupati on the way to his brother's wedding. How can he catch up with the train to cover up his mistake and avoid being banished?