CBSE will conduct the improvement exams in the first week of July. Date sheet and other details of CBSE 12th exam for improvement will be release in the month of June. You have to apply for the improvement exam for Maths and English through your respective school.

See if you want to give exam in English and Maths then u don't have to give practical exam and then u only have to appear in normal board exam if ur score is 75/80 then percentage will be calculated according to it 75/80*100=93.75 which is ur score out of 100. I m not sure but a tentative idea.Gud luck

I am also facing same problem about the 20 marks from school. The subjects are English and mathematics.If I am a private candidate then how will I give the internal assesments of English and mathematics.

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  The application forms for improvement exam will be available in the month of July or August.
  


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  Each form costs Rs. 10 and per subject the fees is Rs. 200
  


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  Forms can be collected from Syndicate Bank branches throughout Delhi and Regional Offices of CBSE for other regions.
  

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  Visit the official website,
  
  http://www.cbse.nic.in
  
  


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  Enter your CBSE board roll number in the first text box
  


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  Enter your 5 digit school number in the second text box and if you appeared as a private candidate and do not have a school, then enter 99999 in place of school number.
  


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  Enter your examination centre number by referring to your CBSE board admit card
  


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  Click on proceed and fill in your details
  


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  Make online payment or through E-Challan from the respective bank
  


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  Note down your application number and roll number that will be provided after payment is done
  


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  Follow the instructions on the confirmation page.