I used to temp in a social services department when the CAF was first introduced and had a lot of input into the form designs and the typing up of the paperwork. It came on the back of, among other things, the Victoria Clambier(sp?) case, where a serious breakdown in communication between social workers played a major part in the girl's death. CAF is a means by which all social workers involved with a client, whatever department/organisation/authority, can use the same set of criteria to assess the needs of that client. As such, a student social worker would be expected to learn how to use it - usually under the supervision of a qualified worker/mentor or senior practitioner.
What a worker puts on the CAF form, be they student or qualified, must be an objective and truthful account of what they have observed. If the client (or the client's representative) believes that to be wrong, then they must take up the matter with the worker's/student's senior or a legal adviser as appropriate.