Do you have to stand for the Pledge?

A student cannot be forced to recite the Pledge of Allegiance, but does a student also have a right to refuse to stand for the Pledge? In this case the student was "called to the principal's office and urged to stand during the pledge even if she chose not to recite it."

UPDATE: I'm thinking that urging the student to "stand to show respect for your country," makes standing during the Pledge more of an expression of belief than it would otherwise be. I can't tell from the article whether the student's objection to the Pledge is to the "Under God" phrase or to the rest of the Pledge.

ADDITIONAL NOTE: Emailers cite a Third Circuit case, Lipp v. Morris, 579 F.2d 834 (3d Cir.1978), for the proposition that you can't be required to stand for the Pledge. We're in the Seventh Circuit, where the most notable case is Sherman v. Community Consolidated School District, 980 F.2d 437 (1992)(which, incidentally, held that "Under God" in the Pledge did not violate the Establishment Clause). In Sherman, the court, citing Lipp, noted that that "no pupil was compelled to recite the Pledge, to stand during the Pledge or place his hand over his heart, or to leave if he would not join in, and that no one was penalized in any way for remaining silent and seated." It then rejected the notion that "peer pressure to conform" amounted to compulsion. It seems to me that being urged by the principal is something more than peer pressure, but not outright compulsion.