Most international schools – over 90%- run on the Northern Hemisphere calendar, that is to say start in August/September and finish around June. International schools also require 1-3 year contracts, and most schools attempt to start the year with a full staff.
January vacancies happen for one of three main reasons:
So the bottom line is that there are almost never large numbers of January jobs. They will happen in expanding markets (expansion jobs), or in areas with longer visa lead times like China.
You may be lucky enough to land a January job, but you will have much more opportunity if you set your sights on an August start.