I have not seen any parents being more likely to produce boys or girls. It is a random thing, but what you are described is common. I've lost a village or two because my villagers would not produce any girls. Then again, my current game, I've had four straight girls. Such is life. You just have to keep trying, but make sure you have a good food source.

As far as the school, you can read about it at this Spoiler thread.
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The VI