(*) Information obtained from Elite Model Management; correct at the time of writing.
For boys, add about 15 cm (6") in height and a year or two in starting age because boys mature later than girls.
For all types of modelling (boys and girls), unless something different is asked for, you should have a healthy, fit, well-toned, well looked after body, flawless skin, and healthy hair and nails.
In the past, weight requirements were simple: thin, very thin. In 2006, the organisers of the 2006 Madrid Fashion Week decided to ban skinny, size zero models. This far reaching and, at the time, revolutionary decision means that weight has become a rather more difficult question: many agencies do not openly state their requirements.