Class of Distinction is a modern series/drama about a family and their relationships. Leon plays the oldest son of the family. He lives with his father (played by Wong Jing), mother, grandmother, uncle (Law Ka Ying), younger brother and younger sister. In the beginning of the series, he works for an advertising agency. However, because of some misunderstandings, he leaves his job and his best friend Jessica urges him to become a substitute teacher at the high school which she teaches at. He agrees, and thus begins his life as a teacher. At first, the students dislike him, but after many trials, they come to accept him and does not want him to leave. Therefore, at the end he decides to continue teaching and does not accept a position that another advertising company offers him.
At the same time, a new counselor, Teresa, comes to the high school. She is Louis' ex-girlfriend. Later on, Leon falls in love with her and they date for a while. Jessica also falls for Leon. After many years of being best friends, Jessica realizes that she loves Leon. In the end, Leon and Jessica remain friends and Leon and Teresa are together. Another humorous relationship which the series focuses on is Wong Jing's relationship with his wife and another woman. He separates with his wife, but at the end, realizes that he loves his wife the most.
Louis dated Teresa while they went to college. Louis was grateful to Teresa's family for lending him money to go to college. However, he does not love her. In Hong Kong, he meets Leon's younger sister and they end up dating. Teresa comes back to Hong Kong looking for him, hoping to get married. However, they break up and Louis stays with Leon's sister.
Jessica also has another relationship in the series. She dates a boring doctor who has an extremely anal personality. He has an obsession with cleanliness. After a while, Jessica can't stand his personality and breaks up with him.