For international schools in Jakarta, I have a few questions please
1- Is there is ranking of BEST international schools in Jakarta?
2- I can not find schools that offer American curriculum as the base !?
3- When does schools start in Aug ?
4- Any tips in how to choose school for 13 and 11 year old ?
There are a number of international schools in Jakarta which offer a range of curricula. You should be able to find several American schools in and around the city, depending on your family's requirements. The school year in Indonesia usually starts in mid-July, but you will probably be able to find a school that will take your children as late entries in August.
Much of the information you need can be found in the Expat Arrivals Jakarta schools guide, which can be downloaded by filling in this form: http://www.expatarrivals.com/guide/jakarta-schools-guide
It has details on all aspects of school life in the city as well as a list of schools, including what curriculum they offer.
Best of luck!