I'm a civil engineering graduate (2015) & got 86.8 %ile in ATMA 2016. Is it worth to join NIBM? How are the placements there?

No, a good percentile does not guarantee direct admission to colleges accepting ATMA scores. Colleges conduct different selection rounds before providing admissions. Many colleges conduct rounds such as Group Discussion, Written Ability Test and Personal Interview. Students who match the ATMA cutoff are called to participate in these rounds. Admissions are offered based on the performance of students in all these rounds. 

No, IIMs do not accept ATMA test scores for admission. IIMs conduct Common Admission Test (CAT) for admission to MBA programmes. ATMA scores are accepted by some of the best BSchools in the country. These include institutes such as PUMBA, Xavier Institute of Management and Research, PSG College of Technology, RV Institute of Management, Jayawantrao Sawant Institute of Management and Research,  KV Institute of Management and Information Studies, etc. 

There is a good chance of receiving an interview call from Christ University with a score of 95 percentile in ATMA exam, but, admission is not guaranteed. Overall criteria includes academic profile, i.e. Class 12, Class 10 and Graduation marks. Other selection rounds at Christ University includes Micro Presentation and Personal Interview. Students have to match all the selection criteria to get admission to Christ University. 

ATMA exam is a nation level MBA entrance exam conducted by Association of Indian Management Schools. Courses such as MS and PGDM are also offered through ATMA exam. The exam is conducted in the CBT test format multiple times a year. The exam checks numerical, verbal and logical abilities of students taking the exam. Duration of the exam is three hours and has MCQ type questions. The exam is accepted by over 700 B-Schools across India, and the scores obtained in the ATMA exam are considered for admission to various management courses offered by these institutes. 

ATMA is a national level entrance exam conducted by Association of Indian Management Schools. ATMA is conducted for admission to MBA, MMS, PGDM programmes at over 700 B Schools in the country. ATMA exam judges skills and basic aptitude of students needed for an MBA or PGDM course.