Astir

[fuzzy-brain]

13d. They will not divide us! (14)
All I have is the 4th letter, 'T'.
This is the magazine of the Association of secondary teachers in Ireland, if that is any help.
I was thinking along the lines of 'Mathematicians' or 'Arithmeticians', but there are obviously many possible answers. However, someone out there may have some insightful ideas. Thanks.
I posted this last Saturday and Mamyalynne suggested 'Multiplicators'.
Any other suggestions? There are no intersecting words. The 'T' is from the sole conjoining clue.

[Mamyalynne]

I hope someone has some ideas - I think I prefer the suggestion of Arithmeticians really.

[Toorak]

I agree with arithmeticians - to do with addition, subtraction, division and multiplication

[Davemano]

Are all the answers linked to education. The list is endless, as you say.
Fortifications - Juxtapositions could fit the clue.

[Neveracrossword]

I prefer multiplicators.

[weecalf]

Contributories could be rivers that join rather than divide doesn’t look right does it ?

[fuzzy-brain]

Thank you all for your generosity of contribution. I am still mystified, although I do like Davemano's 'Fortifications'!