There have been cases of child abuse involving HE families, but they are very very few and far between. "There has never been a case of HE abuse" is a bad line to go down.
Of course there will be abuse among the HE population, although the stats coming out now (google AHEd lies, damned lies and statistics - I think that'd give you the links - HEers have done hundreds of FOI requests to get the actual comparative figures) indicate that the rate is very much lower than in the general population.
But the point of principle to hold onto is:
the current law as relates to child abuse is FIT FOR PURPOSE. Children's Services have the legal powers they need. The fact that they so abjectly fail to use their existing powers with good judgement in cases like Kyra Ishaq is not a good reason to give them more power - quite the opposite. Let them stop acting ulta vires before anyone considers widening the remit of the LA children's services.
Even if 25% of HE families were under investigation by children's services for suspected abuse, that would still not be grounds for demanding access to the home and to the child alone for the other 75% of HE families. Otherwise we lose the principle that the State does not interfere in private life without probable cause.
More than happy to keep discussing any of these issues :-)