I would be more concerned about the lack of information from the teacher than the actual results.
The targets should have been reviewed in the light of the performance at the end of year 3 - taking into account test result & teacher assessment.
You need to know if the test result for maths this year is the same as the teacher assessment - it could be your child just had an off day.
If your child is stressed by the test scenario it might be worth trying a few at home over the summer in as relaxed a way as possible to gain confidence.
You could also ask to see the test paper and note down topics where errors were made - then you can do some work on these over the summer (you will also see if there is an issue with 'silly' mistakes / running out of time etc)
Just because your child is working at a high level doesn't mean they shouldn't be making progress
(taking an extreme view - if the whole class failed to make progress in maths this year due to poor teaching then of course your child would still be in the top set!)
From experience of dealing with teachers you need to try to avoid putting them on the defensive but you do need to be firm about getting information if it appears your child is not making good progress.
Dealing with any concerns at an early stage avoids them becoming big issues next year........
If you really can't make any progress with the school then I would purchase some tests and get your child to do them at home so you can make your own assessment & work on any areas of 'weakness' ready for September.
Hope you manage to get the information you need to put your mind at rest