You might mention eating a sandwich:
Verenice Gutierrez picks up on the subtle language of racism every day. Take the peanut butter sandwich, a seemingly innocent example a teacher used in a lesson last school year. “What about Somali or Hispanic students, who might not eat sandwiches?” says Gutierrez, principal at Harvey Scott K-8 School, a diverse school of 500 students in Northeast Portland’s Cully neighborhood. “Another way would be to say: ‘Americans eat peanut butter and jelly, do you have anything like that?’ Let them tell you. Maybe they eat torta. Or pita.”
The funny thing is that this Portland-area principal seems more racist than talking about eating a sandwich in the highlighted bits ... seeming to imply that it's un-American to not eat sandwiches.
You might use white paper:
Another staple of the classroom - white paper - has also been questioned by Anne O'Connor, an early years consultant who advises local authorities on equality and diversity.
Children should be provided with paper other than white to drawn on and paints and crayons should come in "the full range of flesh tones", reflecting the diversity of the human race, according to the former teacher.
Umm ... somehow I don't think white paper is quite the colour of a typical white person's skin.