From the average score of 86 for boys and 94 for girls in Class A, we can know that boys in Class A: girls in Class A = 5: 3;

Similarly, the boys in Class B scored 95 points and the girls scored 88 points, with a total score of 92 points. It can be seen that boys in class B: girls in class B =4:3.

Then the average score of Class A and Class B is: 89x (3+5)+92x (3+4) ÷ (3+5+3+4) = 90.4 (minutes).