One of the victims has "severely damaged" her eye and has been shifted to Sir Ganga Ram Hospital in New Delhi.
Kamerjahan (26), Ayisha (25), Esha (23) and Sanam (20) were attacked when they were returning from Hindu Inter-College in Kandhal after UP board exam duty yesterday, they said.
The sisters were rushed to a nearby hospital in a serious condition after which Esha was brought to Ganga Ram Hospital yesterday itself.
"Her both eyes have sustained burn injuries with cornea of left severally damaged," said Dr Mahesh Mangal, Chairperson of the hospital's Department of Plastic Surgery.
Doctors said the condition of Esha was stable.