Hello; there are many excellent private schools in London; prep schools start from age 7 -8 (known as Year 3). Your son may be in Year 3 or Year 4, depending on his birth date. There will be a change to 'big' school at age 10-11 (at the end of Year 6) or in some boys prep schools at age 12-13 (at the end of Year 8). Most schools have an exam for Year 3 entry, and there are usually one or two spare places to be found for children coming from overseas into the other Years - give the schools a ring and ask.
It depends on whether you prefer single-sex or co-ed, and which part of London you choose to live in, really. Have a look at the Good Schools Guide website (you can subscribe on-line) and the one for the Independent Schools Council.
There are also several schools that stick to specific national curriculums - American, French, Japanese.
(In addition to which there are many excellent state primary/church schools as well. They are often hard to get into as they are extremely popular. Siblings get priority, and the schools tend to have very small 'catchment' areas so if you rent/buy a
property, enquire at the school to check whether your house/flat is within it.)
Hope this helps.
