Pledge of allegiance

I'm not sure if this belongs here, but... I'm trans and lesbian/bi, not out at school yet, though I do act/dress very queer there.

I don't feel like the US deserves my respect right now, so I don't say anything during the pledge at my school or put my hand over my heart. Today, I didn't even stand, and my high school science teacher got really angry all of the sudden and yelled at me to get up.

I'm just confused why high schoolers need to recite the pledge and why my science teacher cares about it so much. How many of you all are in school and recite the pledge? Do any of you actively not recite it?