Central Board Of Secondary Education [CBSE] — Class 12th result unsatisfied

Respected sir/ mam,
I am not satisfied with my brother's 12th result, he scored Very well in class 10th, in 11 he also have 92.6%, and in 12th he got very less percent, which was totally unexpected. The result which was expected according to the marking pattern of CBSE did not come at all.
And now when we are calling the school principal /director, they are not picking up the call,
please sir/mam, consider my complain.
SCHOOL NAME - Eklavya central school Sulindabad SAHARSA(Bihar)
School No-65443
Please consider my complain its my humble request...