English School part time?

I want to teach English part time and I would like to be able to choose which areas of either Tokyo or Yokohama, which schools are good for this? any recommendations?

You will likely not be able to pinpoint your location in any major city unless you are an experienced teacher already living in Japan and go applying to private schools on your own. Most language-teacher and assistant-language-teacher postitions for foreigners are handled through third party dispatches and temp agencies, meaning you will be placed where there is the most need within a very wide requested area.

INTERAC currently serves the bulk of Tokyo and Yokohama, so your best bet for a general placement in the area would be to apply through them.

It is difficult to get a work visa for part-time work... and INTERAC, as well as most of the other dispatch agencies, as far as I know, only hire full-time workers.