See If you want to get into SSCBS for pursuying BMS and BBA . Minimum eligibility is that you should have done 10+2 from any recognised board. After that you will have to give JAT exam. Your performance will matter. After exam , Group discussions and personal interview round is completed. After that those who are selected are admitted. 

Now JAT doesn't have full weightage . Actually All the processes are considered. You have 50% JAT score, 30% 12th score and 10-10 % from G.D. and personal interview. English and mathemtaics are compulsory.

Thank you.