Congratulations on the interview.
Clothes - smart/tidy. Not a suit! Trousers/skirt and top. Not revealing, no cleavage. Just...normal.
Questions - bound to be one on safeguarding, so how to keep children safe. Such things as check with senior staff, do not ask leading questions, never go and 'sort it out' for them if child protection. You would follow the school's policy.
How you would work with others; supportive, good team player. Keen to learn, motivated etc.
What your transferable skills are e.g. organised, good time management, good at team work, turn your hand to most things, good at (e.g.) filing, displays, cooking, sewing, ICT, numeracy...
What do you think might be tricky? (Friends with parents in class you work in (say nothing, refer them to teacher) issues with your child in school (professional head v parent head etc)
Your own strengths and weaknesses
Examples of when you have done something, e.g. helped someone, something you are proud of.
How would you help a child who... tricky if no education experience so go with common sense. I haven't got direct experience, but I would expect that... if in doubt I would consult the class teacher/colleagues/ SENCo for advice
Likely to be head and at least one other, e.g. deputy, governor or both. Probably about 6/7 questions. If you have got an interview with no TA experience, you obviously did a good covering letter!
God, that was an essay, sorry! Good luck :)