so you were there with 4 other parents, all their children were called but yours wasn't even though you could see him sitting on the carpet ready to go, an then she called the children of parents who arrived after you? and skipped you again?
if this is correct, I would agree with you that it is odd, why would she not call all five children of the parents who are actually there? why skip one? can everybody who is so sure the OP is paranoid explain why this would be? OP is not asking her to remember the order, she is just wondering why is she being ignored when other parents standing next to her are not?
and I don't know why everybody is so shocked at the suggestion that the teacher may be prejudiced, or even racist, teachers are normal human beings, some human beings are racist, aren't they? I am not saying she necessarily is, but it's not a crazy suggestion, is it?
Plus, the suggestion not to speak his language at home is complete rubbish and outdated advice from a time when bilingualism was frowned upon and considered to slow and damage linguistic development, we now know that bilingualism improves cognitive performance in more areas than just language proficiency, so if that is what she really said I would be concerned about her knowledge and capacity to support the learning of a bilingual child. But maybe she just meant to suggest other options for him to practice his English, not that he should not talk his own language? I really hope so! Maybe clarify this at parent/teacher meeting?
OP, I would suggest monitoring the situation, it may have been just an oversight, if it is, then it won't happen again, if it keeps happening, I would make a point of saying to the teacher politely "I am here, I have been waiting a while, could you please call my child?" see what she says!