One of my cousins graduated from NITIE and a few people in his batch had a percentage around the 60s in their 12th boards. And you could find many too.
NITIE gives more weightage to your performance in GDPI rather than past academics at least for PGDIM and PGDISEM courses. You just need to score 97 percentile in CAT for getting a call. Then it all depends on your GD PI performance.
NITIE does consider academic scores in the selection process. However, you can compensate for your poor scores (if any) by performing well in GD and PI rounds.
In a nutshell, I can say that the emphasis on academic scores in NITIE selection criteria is lesser than that in IIMs and many other colleges.