For some children clothing can be irritating. Here are some tips:
find out what is irritating, is it a tag? If so can the tag be cut off?
discuss when the clothing can be taken off and when it needs to be worn eg shoes need to be on outside but can be removed in the classroom, clothes can be taken off for the shower but not at school. Create a social story for this if required.
suggest pressure singlet or clothing item to parents to discuss with Dr or OT.