Asked to do things not on our JD for no more money

[MrsPoppyCrafts]

I am a TA in a special school. I get slightly increased pay and hours for having additional responsibilities. Recently my school advertised for an HLTA job. I applied but didn’t get it. The HLTA Job Description was very detailed and included using an online app to record what the pupil has done in a lesson. The school put on training, but I refused to go. The app isn’t on my Job Description but the headteacher thinks I should be doing it. I went to the union, and got it written into
the job description and the head said he would sent it to the county for evaluation. Apparently it came back as the same pay for me as my job description already says that I should assess and record pupil progress. What should I do next? I am refusing to do it. Will I be told I am not doing my job and be sacked??

Does you JD for being a TA not include a paragraph along the lines of

Recording and reporting of pupils progress under^ the supervision of the teacher.
^
This is common for all TA JD from the lowest grade upwards. The contract doesn't need to state how or that they can't change the method. Just that you are responsible for monitoring and recording pupil progress.