Hey Student,

After completing your class 12 in UP board, you may repeat it again through any other board . But if you wish to do so, then you will have to repeat from the 11th standard either from the same school you are  studying at present or from a different school of your preference

In case if you repeat again , no matter how much you score in the new attempt , only that score stays and considered for your future studies . And the old scores will be wiped out and will not be considered anywhere.