Vaccination is not mandatory and surely schooling is available for unvaccinated children - they are the ones 'at risk' without the vaccines after all.
I would definitely check with individual schools regarding which vaccinations they require - the two preschools that my child has attended have both required vaccination records before she could begin classes. So do most of the international schools. Don't know about the local schools so perhaps someone else can provide info on that.
RE: the unvaccinated children being the only ones 'at risk' - not quite true as they can pose a risk to the community at large by spreading the disease to others (often before identifiable symptoms develop), including infants who are to young to have received a particular vaccination and the small percentage of the population who has received a vaccination which is not effective for whatever reason (for example, the measles vaccine is about 96% effective in the US, so 4% of vaccinated children would be put at risk if they were exposed).
I'm not advocating that anyone do or don't vaccinate their children - it is ultimately a parent's decision, but don't pretend that there is no risk to public health from unvaccinated children, as certainly is. For example:
"The evidence is overwhelming that declining vaccination rates are contributing to outbreaks of disease. Take just one example, measles. The World Health Organization reports outbreaks in countries where vaccination rates have gone down, including France (7,000 cases so far this year, more than in all of 2010), Belgium, Germany, Romania, Serbia, Spain, Macedonia and Turkey. There have already been 334 measles cases in England and Wales this year, compared with 33 all of last year. The U.S. has seen 118 cases as of mid-May, compared with 56 cases a year from 2001 to 2008."
http://articles.latimes.com/2011/jul/18/opinion/la-oe-ropeik-vaccines-20110718