A bench headed by Justice Jawad Rahim had given schools five days in its June 15 order.
"Each of the noticees (schools) is directed to file memo indicating the stage of the work in progress and further time required to complete the work," the bench, also comprising expert member Ajay A Deshpande, said.
The matter is listed for next hearing on July 17.
The tribunal had earlier directed schools to install rainwater harvesting systems in their premises within 10 days. In the event of failure, it had warned, each one would be saddled with a cost of Rs 20,000.
The NGT had earlier directed the Central Ground Water Authority (CGWA) and Delhi Jal Board (DJB) to inspect private and government schools here after a plea alleged that they had failed to install systems to harvest rainwater in their premises.
The direction came during hearing of a plea of Mahesh Chandra Saxena, who claimed to be associated with an NGO working in the field of groundwater conservation.
He has claimed that government departments, educational institutions and residential societies had either not installed rainwater harvesting systems, or had set them up but they were non-functional.