When we answered this question (and I have had this unit signed off with distinctions across the board, so am supposing it was okay!)....we had to mention both summative and formative methods of assessment, such as formal testing / SATS etc which record a childs academic attainment / inteleectual development. But also formative methods such as different child observational methods - target child, tick box checklists, time sampling methods. All would be used in different settings and for different purposes by different people. Teaching assistants may be asked to observe a child whose development is causing concern and feedback to the teacher...they may use the teachers checklist or simply be asked to undertake an observation.
It's important to mention that you would always record / feedback to parents too about the outcome of your findings (via the teacher or according to your role). Yu would compare your observation / SATS / testing results against the expected norms and milestones / expected devleopmental age stats....and use feedback from parents (any concerns shared at home etc)....to then check with class teacher, who would discuss with SENCO in school etc.....and they would then look if any school action / school action plus / SEN interventions were required....
Wth an older child you would need to involve him / her (according to his age and understanding) in any assessment of their development - so recording their feelings wishes and views.....check you are observing them in different contexts (depending on which areas of their development you are looking at - for example social development observe in playground, in group and individual settings etc).
Also take into account their culture / EAL and any issues with these, as it is important to mention you have considered this - a young person may have EAL needs but these may not be creating delayed development (i.e. he / she may not be delayed in areas of their development such as when using their first language).
hope this answer helps!