With very few exceptions (those with current non-JAR ATPL plus a great many hours multi-crew) you must complete an approved course before being permitted to take the exams. Each exam application form must be signed by the CGI of an approved school to certify that you have completed the required course. I think that NAC simply want to see your tuition records so that they can sign your application forms.
We (EPTA) often provide short periods of consolidation training for students from other schools who have failed exams. In such circumstances it is not worth going to the trouble of getting their previous training records. But before signing their exam applications I insist on seeing their results letter for their previous attempts. If they have no such letter I contact the CAA to ensure that they have completed the required training and taken the exams before.