Case
Transphobic parents

Parents don’t want their child to be taught by me because I am transgender. What do I say to them?

Solution #1
This is a matter of discrimination, and if the parents refuse to let their child into your classroom they either have to go to another classroom or you have to move (which I don't think will happen). Try to talk things out first, and involve the school administration so no claims are made that cannot be proven false.

I agree with this solution.

Of course, you should not be discriminated against. But, I also feel that if you are pushing your advocacy for transgender, this can become an issue.

I disagree with the comment above me, as you being who you are is not pushing your advocacy for being transgender. I'm sorry you are dealing with this, but I agree with the solution above.

Solution #2
I would have a heart-to-heart conversation with the parents and say that all you want is what is best for their child and will teach the standards provided by the state. If this continues, I would contact administration and have them contact the parents.
Solution #3
I am also transgender, so I know what you are going through. I would explain to the parents that your gender does not affect the way you will teach their students. I would try to be fair and as kind as possible. If they do not treat you with the same respect, then I would get the principal involved.
Solution #4
Talk to your immediate supervisor. Also, contact your union rep if you're part of a union and your administration isn't handling the situation well.
Solution #5
Communication is king. Try to figure out why this an issue, involve your supervisor. Yet also communicate your side of the story. People tend to have more empathy once there is understanding.

I agree with this solution.