Can a schoolteacher be fired for refusing to say the Pledge of Allegiance?

I don’t like the under god part either, but swearing loyalty to the flag bothers me too. I’d like the pledge to read thus:

*I pledge allegiance to the Constitution of the United States of America, to the ideals it represents and the republic born of those ideals, and swear on my life’s blood to be true to the nation and its people. *