AN OLD friend immigrated from Russia to New Jersey when he was small. When asked if he spoke Russian, he would say he speaks “kitchen Russian”: the kind of things your mum says to you around the house. It’s a good phrase to describe the competence of a lot of immigrants in their “heritage language”. They can argue fluently with their parents about how late they can stay out, but if asked to write a short essay on their three favourite scientific discoveries, they’d be completely lost. First, they may not ever have learned to write their heritage language. If they haven’t read a lot, they also won’t master the kind of formulations used in writing generally.