In reality, the situation is not so simple. His argument assumes that a pupil entered for tier 3-6 answers correctly all questions focused at levels 5 and 6 and incorrectly answers all the (easier) questions focused at levels 3 and 4.
This pattern of performance is unlikely to occur. Pupils are awarded levels based on marks they have gained across all the questions on a set of papers. Our tests award levels which best represent a pupil's performance overall.
Dr Jannette Elwood Principal officer Key stage 3 Qualifications and Curriculum Authority 29 Bolton Street London W1