I taught with Caledonian School on-and-off for about 2 1/2 years. I began by first earning my TEFL with their program, and then continuing to teach with them through their job guarantee. At the time, it was only necessary to achieve a Pass-2 in their program to be guaranteed a job afterward, though I believe you have to get a Pass-1 now. The truly great thing about Caledonian is that if you can get a job with them as a non-EU national, they will help you get your work permit and visa. This is becoming increasingly rare for jobs in Prague, especially with the economic crisis. You also don't need a great deal of experience to work for them.
Some of the positive aspects of working for Caledonian are:
-Great teacher resources and support. They have an extensive library and it was not difficult to find someone to help you troubleshoot a class or offer suggestions. They also have plenty of computers and Internet access, though the limits on their copiers and printers can be really annoying. Teachers are also divided into groups with a "senior teacher" who runs periodic seminars and offers assistance if you need help.
-Generally, the atmosphere is quite positive. While I was there, it was easy to make friends and get connected, even if you were new to Prague.
-The pub was an excellent addition to the atmosphere. It was open all day and directly across from the Teacher's room, and offered everything from coffee and tea to daily lunches and alcohol. I have a lot of great memories lesson planning and socializing there.
Some negative aspects of Caledonian are:
-No yearly paid holiday leave until you have been there at least 3-4 years. This can really be a strain on your budget during Christmas and summer holidays.
-The insurance is a bit dodgy. We aren't offered the state insurance, so it's not accepted everywhere.
-Their scale for calculating raises has changed a few times, and they have now instituted a complicated "point" system based on student reviews, success rates, and observations.
As with any language school, another difficulty is budgeting and determining your income. I found the pay to be reasonable... you are paid for the hours you work, and you get paid for late cancellations from your students. However, if your students cancel early or it is a month with a lot of holidays, some months can be extremely difficult. In addition, you aren't paid for travel time, and teachers spend a lot of time on public transport.
All that said, if this is your first job in Prague, I would strongly consider this school. They have a huge network, and if you need experience and a visa, they can help you with it. And if you need a TEFL, they can help you with that, too. People have said negative things about Caledonian since they merged with Tutor, and I can attest that the atmosphere isn't what it used to be. And if you have a lot of experience or EU citizenship, you can probably look elsewhere. But overall, I enjoyed my time with Caledonian, and would recommend it as a good place to start building a life and career in Prague.