What would you do if you suspected a child was at risk of harm/being harmed/made a disclosure to you that you were worried about?
You will definitely get a question along those lines. The answer is to tell the designated teacher for child protection and record it appropriately. Or something along those lines. It doesn't need to be a fancy answer because the above is what they want you to do and they also want to know that you're not going to conduct your own mini investigation.
You will probably have something along the lines of:
What is your understanding of the role of a teaching assistant?
You will be working closely with the class teacher/other teachers in the year group/key stage. How will you go about ensuring good relationships within the team?
Look at the person specification again. Make sure you have an example to offer of your experience for each of the points on the person spec. Make sure you know your 'personal statement' bit of the application form inside out and can elaborate on the evidence you gave in that.
Remember, you've already impressed them because you've got an interview. All they want to do now is cross the Ts, dot the Is and make sure they get the right person for them.
Oh and make sure you smile and look the interviewers in the eye, don't be afraid to ask them to repeat a question or take some time to think about it or to come back to a question later. Don't make jokes, but come across as human and someone that they warm to. They want someone who's looking out for their kids.
Good luck x