I think Ofsted might ask questions if a lot of children failed as to the appropriateness of the test entry.
A child must be working 'above level 5' for entry to be appropriate.
Schools have to apply for copies of the paper for the number of children that they want to enter in advance so there is some guesswork going on as to which might be capable of the level 6 at the time of ordering the papers. Also the standard for achieving it possibly varies from year to year so there's nothing too hard and fast.
Apparently there are a lot of myths about which children can be entered across different primary schools. A government funded piece of research has been carried out into the different reasons primary schools don't enter children for level 6. I'll try find the link later this week. Schools invent their own criteria when there are none laid out.
OFSTED shouldn't really care two hoots if a child has been entered who didn't pass because it really doesn't matter. OFSTED should be bothered if there are children not achieving higher levels in a school who could have done.
In the new KS2 tests (for the new national curriculum) there will not be separate higher level papers (in part because levels are being scrapped) but the papers themselves will cover the equivalent of the higher levels somehow or other (another of those mysteries of the future). This means that the different entry criteria that different schools spend their time devising and applying will no longer be needed.
Good luck convincing your school in the meantime Silverysea. I'll try and dig that thing out for you as you may find it helpful in your discussion with school. A lot could happen between now and May but I bet a lot of schools have already decided which children not to enter. From what you have described of your school Silverysea I think you might be banging your head on a wall. They clearly have fixed ideas about children's capabilities and their own way of interpreting government guidance which are hard to change.
Maybe try asking on TES primary forum for some good materials to cover the high level 5 / low level 6 ground at home in the various subjects in case your child is not included in their arbitrary, but probably apparently "scientifically" developed list of children suitable to be educated to this level and entered for the test.https://www.gov.uk/government/uploads/s ... -RR279.pdf