They only have Chinese subject starts from Grade 9. It's better to come as early as possible but not later than a certain date (about early June, please check the website of the school board). Because if you come before the close of the schools, you will know which school your kids will go to, otherwise, if there is no space in your catchment school you may have to wait until the end of August then you will know which school you kids will go to. If you decided to come here for good the examination in Hong Kong is not important, you don't need the school result to apply for school in here. But the thing is you need to have a residential address in order to go to the catchment school, i.e., you need to have a proof of your address, just like rental agreement or purchase agreement, so you need to find a place before you go to apply for a school and you also need to have an ESL assessment at the school board later on.