Gender

When talking about gender we first we have to make sure to distinguish the difference between gender and sex; sex is defined as the biological dimensions of being male or female. Gender is the socio-cultural aspect of male or female. Gender generates an expectation of how a person should feel, think, act in society based on their sex this is known as gender roles.
When a child is growing up they are learning from adults and role model how they are expected to act in society.  By watching how people are rewarded or punished for the way they act. There are two theories on how children develop their socio-learning theory on gender: the Cognitive Development Theory, and the Gender Schema Theory .
The Cognitive Development Theory states that a child learns different concepts of gender and comes to see gender as a consistent. 
The Gender Schema Theory believes that a child develops a concept of what gender is then as time goes on they blend those gender concept with with their own self gender concepts.
I see the gender schema theory as being more accurate especially in today's society where it is more accepted by society for girls and guys to take on roles of the opposite sex.
As teacher we have to be aware and be careful no to cast or teach stereotypes, gender biases or sexual orientation issues.  This can be difficult as each person has their own belief on how gender should act or behave and as time goes on what we believe is accepted behavior may not be what the next generation sees as normal behaviors or attitudes.