Can "them" be used to replace a singular noun?

I recently got a permission slip daughter's school. It contained the sentence: "If your child misbehaves on the band trip, you will have to drive to Dallas to pick them up." I think that it contains a mistake because them is used to replace child. Child is singular. Them is plural. The sentence should have been written: "If your child misbehaves on the band trip, you will have to drive to Dallas to pick him up." From what I understand "him" is singular and can be both masculine and neuter. there seems to be some issues with using him in these times if increased awareness of the need for gender equality. I suppose that we as parents of a girl might have thought this was wrong since our child is "her". Parents of boys might have been offended because they might think that the statement implied that any child who misbehaved would likely be male. How do you think the question should have been written?