I know that some 6th form dancers do no A levels but take all the dance classes on offer. It is very much up to each student how many, if any they do. Of course, at the end of the course, the students get the Trinity Diploma which can be converted into a BA so it is not necessary to take A levels.
If the head of dance has to report on each solo and they are only one minute long, then she has to write sometime. I think that the solo is important for those who are they are not sure about. If it is an easy 'yes' or 'no' then the decision is probably already made.