Tug, if you are going to use one expression out of several pages in a report that I linked to for information, that is your right.
i do not know why they chose to use it, but you found a note explaining it so there was no deception.
I suspect that many of the pupils you taught were of immigrant families but had been born here and had some years in English schools.
Here is a BBC report on the issue so that you can not pretend that it is not an issue.http://news.bbc.co.uk/1/hi/education/7372853.stm