Typical interview questions for a school admin officer - How would you deal with an angry parent? - stay calm, don't mirror any aggression shown to you, remain professional and sort out the problem.
What would you do if a child reported an incident of abuse to you? - all schools have a designated Child Protection Officer who you would report the incident to. You would listen carefully to the child, take them seriously, report to the Officer, make a written statement if requested, then treat it as confidential and basically never discuss it again unless asked officially.
The school will want to see that you are aware of the importance of confidentiality, Data Protection, Child Protection and Health and Safety.
The tests will most likely be word processing and Excel based , probably very simple, so don't panic.
Remember it's an achievement these days to be called for an interview!