Though you have 2 years full to go for AIPMT EXAM, you can focus from this year. But remember to concentrate first on Class 12 Board Examination which is very important for AIPMT exam point of view.
You can devote at least 2 hours for entrance examination studies while ongoing school curriculum.
You can increase your preparation time at the start of 2015 to speed up your school based curriculum and medical entrance exams.
You need to know the fundamentals of every chapter of Biology NCERT Textbook.
Give equal time from now to lessen your pressure...
BEST OF LUCK...