It could be anything, but the good news is that a second interview always means you're in with a chance. Someone likes you and sees the possibility of hiring you.
Best option is that they have already pretty much decided to hire you, and will make an offer more or less straightaway.
Or they could be close to offering but want to tidy up a few last points first. Answer their questions, and the offer might well appear before the end of the meeting.
Or it is truly an interview. You've passed the first stage, and now they want to explore more. Questions might be a little harder, or not. They could have identified some areas where you might have less experience, and they want to explore how you'd approach that. So before going in, think long and hard about any ways in which you are not a perfect fit. You're younger than most teachers in the department? It's your first post of responsibility? You aren't trained in some key program? Networking will be key, but you haven't demonstrated that skill in your CV or first interview? Whatever it might be, be prepared to discuss it and have some plans ready. Also be ready to listen. They might have suggestions about how to tackle these issues, and you should be open to them.
My school occasionally needs three full interviews and a fourth meeting to put forward the offer. Usually though, the offer comes in the second or third interview. Good luck.

I disagree that better schools tend to be more relaxed on teacher dress. The best school I was ever in, also has the strictest dress code.
Much is cultural. In Qatar, as mentioned, it's a big deal to dress properly. And properly in this context tends to mean conservative and formal.

Flexibility is great. Overreaching is not. "I can teach history, economics, physics, swimming, maths, arts and French" is ridiculous, unless you actually have credentials and experience to back up that claim. You may laugh, but I see far too many applications for posts that are completely unsuitable based on credentials and experience. Most often, it comes down to a complete lack of understanding that passing high school chemistry is not adequate preparation for teaching high school chemistry. It makes one sound foolish to suggest that one can teach well beyond one's demonstrated scope.

I disagree. With the advent of google docs and suchlike, it's very easy for a school to keep a single register of all applicants, even if multiple people are doing the screening.
I go through tons of applications as part of my workload. I have to read each carefully and make suitable notes on our school's register. I dislike multiple applications. If you can teach more than one post, I'll note it. If you want to be considered for more than one post, say it. Even if you don't say it, I'll probably pick up on the possibility from your overall CV, and I'll know what's available in my school (probably better than what's posted on various websites, since internal movements and hirings and late resignations might not be updated yet externally), and I'll make a note in my summary.
If you send multiple applications, It won't change the situation, it'll just give me more work since I have to visit your file more than once. When faced with a couple hundred applications, efficiency is very much appreciated.

I've said it before and I'll say it again.
Some admin are cads and behave badly. I think they're by far the minority.
Some teachers are equally badly behaved. Also by far the minority.
I don't approve of either group's behavior, nor do I use it as a pretext to explain away my own or anyone else's bad behavior.

Our school would count it, and I think most others would too.

It doesn't seem so long ago that PG was claiming to be admin and a recruiter. But this season, he's very down on admin and recruiters. Hmmm....
Don't go back on your word.
Schools do talk. And you're talking about schools in the same country. I can't speak for the UAE, but where I am, the school admin types have regular gettogethers to discuss shared issues. And that's just the official get togethers, not the social ones.
Even outside the country, people talk.
At a recent fair, my friend and I were courting the same applicant. We knew it, but he didn't know we knew. We just did our own thing and let him make up his mind. (This happens every year i go recruiting, by the way, which is not always every year.)Imagine the fireworks if he tried now to switch schools.
You just can't know who knows what or whom.

To clarify...
The first year out of the US, you'll need to use the physical presence thing, which means staying out of the US for 330 out of 365 days. Those days can start anytime, doesn't have to be January 1. So if you move to Argentina on August 10, your 365 days start then. Be careful how much vacation you'll plan for home.
After that, you can use the resident thing, and spend as much time in the US as you want.
And always, the amount of your exemption is based on how many days you're out of the US each tax year. If you're out all year, you get the full exemption. If you go to the US for 5 days in 2013, your exemption will be 360/365 of the maximum exemption. Etc.
And I can't recommend fibbing. I personally know two people who have been caught out, and it cost them 10s of thousands to get right with the government again. Since you won't be paying anyway, or paying pretty little, what's the benefit of lying?

If your housing is provided directly by the school for 'your employer's convenience', you don't have to count the value in your income. But if you take a cash allowance, you have to count that. Check with a tax specialist to see if your housing meets the 'convenience' standard. It can save you a bundle.

Disagree a bit. IB schools usually want experience, but they don't always get it. Sometimes there aren't enough candidates. Sometimes the IB newbie has better qualities than the IB experienced grump. Big schools can train you as easily and maybe easier than the little ones.
Go for it. If newbies didn't keep getting hired, the IB wouldn't have to keep offering training to hundreds of newbies every year.

It's more common not to pay taxes.
But in the EU, more common to pay.
You have to ask.
And many schools will say 'tax free salary' in their recruiting info. That helps.

First person. Third feels odd.

Disagree.
Fairs are chaotic experiences. Once is plenty. You won't get more out of two than you get out of one.
Your new school will NOT like you going to another fair. They want to know you're committed, and whatever words you say, the action of attending a fair speaks volumes. At some schools, the act of attending a fair is considered an official letter of resignation.
Recruiters at the fair will not want to talk to you. Our time has ridiculous demands on it during a fair. We work often from 7:00 to 21:00, interviewing, checking references, following up with spouses, conferring with colleagues back home, smiling and chatting in hallways and elevators because you never know what will make the difference as a candidate is gathering their info. Lunch is often a mythical creature. Not complaining, mind you, but that's how it is. And it's no better for most candidates.
Stay home. You'll be happier.

First things first, stop looking at that table. That's for non-US citizens living in the US. Doesn't apply to US citizens living abroad.
Each country is different, and even schools can be different within a country.
For example, a country might have granted an exemption to teachers at a particular international school, but not to other schools. So you need to check each country and school as you apply.
In many cases, you will not need to pay, or even file, taxes in the country where you live. Sometimes this privilege expires after a certain number of years.
In many cases, it's the other way. You will need to pay taxes in the country where you live.
In Germany, it used to be the case that your German taxes would be taken out from day one, but if you left at or before the end of two years, you'd get the whole whack back in a lump sum. I'm not sure if this continues, or if it applies to all schools.
No matter what, you need to keep filing taxes in the US. Every year. This shouldn't be a problem. You'll get an exemption up to some large amount of overseas income, like $85,000, so you won't be paying taxes, just filing. You may have investment income or such that you'd still have to pay taxes on.
You might be able to invest in an IRA, but not a 401k. Some schools will help you with a retirement contribution to an official account, but this is very individual. Other schools give you a lump sum yearly to do with as you will. Up to you whether you invest or spend. Others still will give you an end of service bonus, which would be again your choice what to do with. Others just give you your salary and planning retirement is up to you.
Whatever you do, you'll need to take more responsibility for planning retirement than you would usually need to do back home. And with the better packages, you could do quite well if you plan and save.

Some schools are not very supportive at all. You might well find yourself on your own, or almost. The school might just tell you what to do, for example, and leave you to go do it.
Salaries tend to be quite low and packages even lower. Are you sure you want to do this? You might find Italy more fun if you were living elsewhere, making money, and visiting Italy.