As you will know, two teaching unions have called strike action for next Thursday 17 October. Employees are not obliged to inform their employer if they intend to strike, so it is difficult for the school to know with any certainty who precisely will be in work on that day.
In order for you to have time to make arrangements for childcare next Thursday, I understand from the information I currently have available, that the school will most likely close to pupils on the strike day, as there will not be enough teachers to take classes and supervise the pupils.
I hope to have a definite response to you early next week, but in the meantime you should make arrangements for your child to be off school on Thursday in the likely event of closure.
The strike action is not against Priory School, but the government and is part of a national programme of industrial action.