400 is not extremely low score for nurture student in Allen.
Do hard work for rest 1.5 years and it will certainly pay back.
Be consistent with your study. Study everyday no matter what. Do something everyday to achieve ur goal.
In enthusiast (12th) ,u will surely improve and even will get 600+ if u donot give up on study now.
Being nurture student, u may have difficulty due to exam pattern…but trust me in enthus u will get used to exam pattern.
Work hard…solve as many MCQs as u can.
Solve physics module 2–3 times to get decent score in physics. Read ur physics notes many times.
Read bio NCERT thoroughly. Try to correct all the bio questions which are from NCERT.