Greetings

There is no need to calculate the percentile score in the separate categories because once the percentile is courses are calculated in the bulk of all the students then the ranks may be prepared from that list category wise also so there is no need to convert in segregate students based on their categories is this will reduce the data size and will not reflect the exact results therefore the percentile score will be calculated in general and letter the ranks will be prepared on all India basis and also on the category basis.

Hope this helps all the best