Hello dear,
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Admission for BA psychology in St. Joseph collge Bangalore is based on interview . And interview is based on the percentage you score in 12th
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Let us firstly check Eligiblity criteria,

• Candidates who have passed 2 year pre-university examination Conducted by Karnataka education board
• If not, any other examination which is equivalent by Bangalore central university shall be Eligible for Admission.

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Now, a clear Eligiblity criteria will be mentioned on February 2020 on official website. Here is the link for official website of college.
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http://www.sjc.ac.in