Assume your dataset name is class. Try the follwing simple code.
proc sort data=class out=class_sorted;
by chinese english math;
run;
data class_grouped;
set class_sorted;
group_10 = int((_n_+10)/10);
run;
proc sql;
create table class_mean as
select group_10,
mean(chinese) as ave_chinese,
mean(english) as ave_english,
mean(math) as ave_math
from class_grouped
group by group_10;
quit;