I think this refers to the term "Novice monks". Any boy under 20 years old cannot be an actual monk. The minimum age you have to be is 20, but you can be what is called a novice, where you don't take on so many rules. You can start very young, at least around 6 years old. The man who does the maintenance work here, his name is Maha Tong, he first came to the Wat when I believe he was 12 years old. He was a novice for 8 years, then when he was 20, he became a monk for some years. So a novice is a person who is under 20.