I know that when I was in school, I always would stay seated. I never liked the idea of pledging any sort or allegiance to so something I don't believe in. I always got yelled at by the teachers and made fun of by students, but I didn't care.
The Pledge of Allegiance of the United States is an expression of allegiance to the Flag of the United States and the republic of the United States of America, originally composed by Colonel George Balch in 1887, later revised by Francis Bellamy in 1892 and formally adopted by Congress as the pledge in 1942. The official name of The Pledge of Allegiance was adopted in 1945. The last change in language came on Flag Day 1954 when the words "under God" were added.
Pledge of Allegiance text:
"I pledge allegiance to the Flag of the United States of America, and to the Republic for which it stands, one Nation under God, indivisible, with liberty and justice for all." More: en.wikipedia.org.
Stand, yes. It is a sign of respect to your host country and hosts - yes, even your own country - to at least stand during the recitation of the national pledge. That is for ANY country, even those not your own!
As far as reciting the pledge and saluting the flag, that should be a personal choice.