of Public Works Department manages the drinking water supply in the state. Schools and Anganwadi Centers have been specifically targeted to improve drinking water supply as well as attendance to these institutions. Many areas of Tripura have the problem of excessive iron content in groundwater requiring the installation of Iron Removal Plants (IRP). Tripura State has received the best State Award for Water & Sanitation under the category of Small States in the IBN7 Diamond State Award function for doing commendable work to provide drinking water supply to the people with the sparsely distributed tribal population in hamlets of hilly regions of the State. However, a study by the DWS Department found a depleting water table and excessive contamination. Still, packaged drinking water under brands "Tribeni", "Eco Freshh", "Blue Fina", "Life Drop" and "Aqua Zoom" among others is manufactured and sold in the state. Filters of many types and brands, in addition to locally manufactured ceramic type filters, are sold in the state although their acceptance in rural areas is less. Education As per 2011 census, the literacy rate of Tripura was 87.75 percent, the fourth-highest in India (which had a national literacy rate of 74.04 percent). A state government survey in 2013 announced that Tripura has the highest literacy rate in India at 94.65 percent. Schools in Tripura are run by the state government, TTAADC or private organisations, which include religious institutions. Instruction in schools is mainly in Bengali or English, though Kokborok and other regional languages are also used. Some of the special schools include Jawahar Navodaya Vidyalaya, Kasturba Gandhi Balika Vidyalaya, residential schools run by Tripura Tribal Welfare Residential Educational Institutions Society (TTWREIS), missionary organisations like St. Paul's, St. Arnold's, Holy Cross, Don Bosco, and St. John's. The schools are affiliated to the Council for the Indian School Certificate Examinations (CISCE), the Central Board for Secondary Education (CBSE), the National Institute of Open Schooling (NIOS) or the Tripura Board of Secondary Education. Under the 10+2+3 plan, after completing secondary school, students typically enroll for two years in a junior college or in a higher secondary school affiliated either to the Tripura Board of Secondary Education or to other central boards. Students choose from one of the three streams—liberal arts, commerce or science. As in the rest of India, after passing the Higher Secondary Examination (the grade 12 examination), students may enroll in general degree programs such as