The increased competitiveness of schoolboy rugby has resulted in the players becoming bigger and stronger. For example, the average body mass of players at Craven Week has increased by 10 kg (6.6%) since 1968.
It is clear that the heavier players have a competitive advantage, or from another perspective, one can argue that the smaller players are at a disadvantage when it comes to being selected for high-level teams.
For example, a 50 kg boy with 10% body fat compared to the same size body with 20% body fat is going to be at an advantage because he will have more muscle and therefore be stronger and more powerful than the boy with greater body fat percentage.
Secondly, children matched for body mass may not necessarily be matched for psychological, cognitive and skill levels. Therefore, while the competitive advantage may be removed from differences in body sizes, new competitive advantages may be imposed by different levels of these other factors (psychological, cognitive and skill) that are also important in sport.
Thirdly, a problem which always accompanies weight categories in sport is that of “making weight” – i.e. crash dieting, saunas and the use of diuretics to meet certain weight requirements.
Fourth, and a more logistical problem against weight categories, is that many schools will not have enough players to make a team if they have to subdivide teams into weight categories.