Since your wife started earning from this october having monthly income of Rs20000 pm. Therefore, total income from october2012 to march 2013 comes to Rs120000 . Rs 120000 is treaeted as turnover/ gross receipts therefore deduction is allowed under sec 28 to 44AD of the Income tax Act, 1961.
Moreover it is not necessary to file income tax return because basic exemption limit applicable resident women is Rs200000
It is not necessary that income shoul be deposited in seaprate bank account it can be deposited in savings aacount of your wife.
However it is advisable that if your wife is giving coaching under some name like "Sai Tutorials" etc then you can open a bank account but this is unecessary burden . Therefore you can continue to deposit the money in your wife savings account.