Also remember primary HTs don't care about how their pupils do inY7 or GCSEs or life. They only care about their school stats.
They aren't protesting the spelling test because it's bad for the pupils but because it's bad for the HTs
If they cared about their pupils they would have taught them to spell, including their dyslexic pupils who are very hard to teach.
this emphasis on spelling in SATs will almost certainly improve the teaching of spelling in lots of schools. Which so far has often been dire.
Certainly my DD was put on the most dreadful spelling interventions (eg wordshark) purely so they could tick a box saying she was on a spelling intervention.
But there was never any real intention to teach her to spell.