If the ratio of girls to boys in the school is 5:6 and there are 20 girls in fifth grade, how many boys are in the fifth grade?
If the ratio of girls to boys in the school is 5:6, the total ratio of girls and boys is 5+6 = <<5+6=11>>11
If there are 20 girls in fifth grade, the fraction representing the number of girls in the fifth grade is 5/11, and since there are 11 boys, the fraction representing the number of boys in the fifth grade is 6/11.
The number of boys in the fifth grade is 6/11 * (20 girls) = <<6/11*20=10.909090909090908>>10.909090909090908 boys. Answer: \boxed{10}.