This is an appalling situation.
For the children sitting behind, annoying and off-putting, but appalling? Every now and again, a question pops up on here asking how a child who has special needs can be assisted in an entrance test. There is provision for this to be done set out in the guidelines - say a blind child who is (in this case) musically talented wants to take the test - it's perfectly fair for them to have an adult assistant, and this would normally be done in the same room as others taking the test - although sometimes extra time may be given to allow for the time lapse in working out the answer & telling the adult.
Maybe the answer would to have put the child being assisted at the back of the room? Certainly not in a separate room, as then people would complain that they were either unsupervised or given 'special privaleges'.
I know nothing of this particular test - is it a music theory test, or academic? I would imagine that the pass rate from this test would be fairly low if they then go onto an audition, where they can filter out the average from the exceptional.
I failed my audition for the Royal Acadamy - perhaps I should have started learning my 2nd instrument a little more that 3 weeks before the audition - but I did pass the entrance theory exam, and assume that this is similar, but at a lower level.