What do you mean by the best ESF school?
All ESF schools are run by the same head organisation so technically there shouldn't be a 'best,' one.
Different schools are popular for different reasons and suit different children. For example, by 'best', do you mean has an excellent academic record? Has the best sports facilities? Is famous for its emphasis on music and drama? Has small class sizes? Encourages parental involvement?
Am sure you will find everyone has their own favourite/best school.
You will also find that many ESF schools, have waiting lists, espec. those that are the most popular.