I doubt whether the authority would instruct schools not to release these figures.They can be obtained, if necessary, under the Freedom of Information Act. (See the thread "Any idea how many were successful in the 11+ this year??")
she said that such information would be used against the student if their exam score was marginal. She repeated this assertion to one of the parents in a later conversation. The implication was that a child could lose a Grammar School place as a result of having been ‘shopped’.
I don't believe for one moment that a place could be withdrawn in such circumstances. (If it did ever happen, the parents would probably appeal - and I've never heard of such a case coming to appeal.)
It's more likely that the implication was that the authority would use the information against the parents at an appeal, if the result was a marginal fail
. Again, I've never heard of such a case.