The female child is not valued more than the male child in Kerala, she is valued equally.
I can quote from my personal experience. When my wife was pregnant, I was slightly partial towards having a daughter while my wife was partial towards having a son. I was partial towards a daughter because I have seen how much my sisters are attached towards my father and what great company they are when compared to me. My brother and sister both have a girl, and having seen how great they are, I was partial towards having a girl for myself. But when my son was born, all that was gone in an instant. All I ever wanted was a son like him.
Having said that, the status enjoyed by women in Kerala has a lot to do with the culture of Kerala. Many prominent communities in Kerala, especially Nairs, follow matrilineal system. This line of succession through the female line meant that female child was valued because of compulsions of economy.
Have no doubt, Kerala society is also patriarchal. However, education and rise in income combined with rule of law has played a major role in toning down the effects of patriarchy in Kerala. Women are independent, educated and are heard in the society. The success of Kerala society, intentional or unintentional, has been to eradicate the disadvantages that women face elsewhere in the country, i.e there is no economic or social disadvantage that you face by having a girl child.
In my family my mother is the most educated. My sisters are more qualified than I am. They are more independent and better at making quality decisions. My wife is more qualified than I am, well travelled, well read and even smarter than I. Women in my life have always performed better than I have done given the same opportunities. I am not implying that they are better than men, but they probably understand the value of the opportunities presented to them more than men do, because it comes easy to men ( probably due to patriarchy).
Given all this, why would anyone consider having a boy better than girl? They wouldn’t unless they are illiterate or socially ignorant. We have taken care of that a long time ago itself.