I scored 86% in 10th, 89% in 11th ,bt 64% in 12th..?

i was thinking to write my 12th boards again but due to family problems i didnt write .. and joined some normal college ..n now evryone is telling i could have joined reputed college.. im thinking to rewrite 12th exam so can get in to reputed college .. is it possible to join 12th again after doing 1year btech?