In Scotland it is nearly the same in the primary school age grade can be mixed teams and what is the equivalent of U13 is when there is segregation. Dixie gets it right, especially about the hard work required to get numbers for girls teams. In Scotland they are U15 for girls, so playing with 3 year groups, and then U18 again with 3 year groups. I, and a few dads I have spoken to, believe that this makes it hard on U13 girls who have to play with up to U15 girls and feel that there should be a bit more flexibility so that girls at U13 could continue to play alongside U13 boys.