In the Senior School (Grades 10-12) students can opt for honours courses by subject domains, a system known as 'setting' rather than 'streaming'.
That a student has not been in the honours class in the Junior School does not prevent them from attempting the enriched classes later. Determination of honours classes rests very much upon student performance and teacher recommendation. Mobility, of course, is the essential factor so that if placement is proven to be misjudged, then the student can be moved to an appropriate class without loss of progress.