NATA is a National entrance examination conducted by CoA to get admission with B. Arch. , not an institution.
NATA, National aptitude test of architecture, is an entrance exam which is conducted by National Institute of advanced studies in architecture (NIASA) the body of council of Architecture in India. This entrance exam is a national level examination. Students who are willing to study Bachelor of architecture or some other relevant architecture courses at all recognized institutions across India, can give NATA after their 12th examination.
So, NATA is a national entrance examination. And institutions which are affiliated with NATA, take admission on the basis of NATA's score.
More than 379 institutes are there all over India, empanelled by CoA which offer admission in B. Arch course on the basis of candidate’s score in NATA. Approximately, 21,458 B. Arch seats are available all over Indian institutions.
If you are willing to prepare for NATA, you need to check the institutions affiliated with NATA and choose your own preference.
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Check out how to start preparation for NATA,
https://designfresher.com/forum/question/how-do-i-start-preparing-for-nata