The IIT JEE consists of 2 Tests viz. JEE Main Test and Advanced Test which test problem solving ability in basic science subjects - Physics, Chemistry and Mathematics. IIT JEE Main Test is for 3 Hrs. while IIT JEE Advanced has two tests of 3 Hrs. each.
Only the top 2,50,000 (approx.) candidates (including all categories) based on the performance in JEE Main will qualify to appear in the JEE Advanced examination, provided the candidates are among the top 20% high scorers of their respective boards or have atleast scored 75% in Std. XII board examination.
As the above selection pattern gives a substantial importance to the Std. XII Board marks, it is very essential that every student prepares well not only for the IIT JEE, but for Std. XII also.