National Curriculum only sets the framework ~ the teachers decide how it is implemented in each lesson.
In this case the NC would say something about recognising "Word Families" (as they like to call them) and the teacher will have selected the words she would use to illustrate the point.
Whilst I personally object to the 600 plus pages of the National Curriculum (Compared to less than 30 pages in Sweden) as a principle, I object even more strongly to it being used as an excuse by poor teachers.