The Lower School comprises the Den, Lower 1 (Reception), Forms 1 and 2. The Upper School comprises Form 3, Upper IV, Upper V and Upper VI (years 3-6).
The classes are kept to a size designed to ensure that each child benefits from a communal environment whilst at the same time receiving considerable individual attention.
There are approximately 20 children in each class. Every class has its own form teacher, and in classes up to Form 2 there is also a full-time student teacher.
The school also employs a number of additional qualified teaching staff, to ensure that children in need of individual attention, receive it quickly and effectively.
Children enter either the youngest class, the Den, at the age of three or Lower 1 (Reception)
when they are four. They move up a class each academic year. Although in the past boys left for their next school
at the age of eight from Form 3 (or Form 2 if going to Latymer Preparatory School) boys are now expected to remain at OHS until the age of 11. Both boys and girls leave
for their senior schools at the age of 11 from Upper VI.