Who are more smarter girls or boys?

I would say neither. Intelligence is an individual characteristic, and it plays no favorite according to gender. Historical Example: In ancient Egypt it was customary to have a male ruler, even a feeble-minded one, and even if more capable female heirs were available. This custom was continued by the invading Greeks. Ptolemy XIII and his sister Cleopatra VII were both products of a family which had been practicing incest for more than two centuries, but it took an invading Roman to realize that Cleopatra was gifted with much more brains than her brother, despite the fact that she was female.