The kids already have a range to fall within. 40.1 to 43 = 43 lb weight class. 43.1 to 46 = 46 pound weight class. 46.1 to 49 = 49 pound weight class, etc. That is why they establish all the various weights. The kids are going to grow during the season. So if in November your child weighs 45 or 46 pounds - there is a very good possibility he or she may need to be in the 49 or 52 pound class by March. It is that simple - they will grow during the season.