S2 = 1 10×( 100+ 100+ 100 = 100+ 100)= 60，

The average score of Xiaoying is (60+80+70+100+50+90+70+90+100+90) ÷10 = 80.

The median is 85 and the mode is 90.

∴ 80,60 first line 80,85,90 second line ((5 points), 1 minute per space)

(2) Xiaoying's excellent rate is 510 =12,

Xiao Ming's excellent rate is: 310 = 310,

∵ 12>3 10,

The student with high excellent rate is Xiaoying.

So the answer is Xiaoying.

(3) Not only that, such as: Xiaoming still needs to work hard to further improve the excellent rate;

Xiaoying's study should be persistent and steady. (10)