How much weight is put on senior year grades??? please help!!!

<p>Hi, I've been having a senior year crisis right now and was wondering really how important senior year (quarter) grades are?</p>

<p>First quarter:
AP econ: B
AP Stats: B
AP Chem: B
AP Lit: B
AP Calc BC: A
Spanish 9: B</p>

<p>If my second quarter grades look like this:
AP econ: A
AP Stats: A
AP Chem: A
AP Lit: A
AP Calc BC: A
Spanish 9: A</p>

<p>How badly would this midyear report affect my chances at top 20 colleges? Schools I am applying to include CMU, Berkeley, Harvard, Cornell, and UChicago. please help!!</p>

<p>P.s. my GPA is like a 3.9; senior year grades do not go on your transcript.</p>