The problem is that if you are the kind of parent who is interested in parenting classes you are probably the last kind of parent who needs them.
When my sister had her son she lived in what is termed a deprived area of London, never mind that she had a lovely house and good job, there was enough social housing around to earn her neighbourhood this dubious honour. As such she was able to attend a Sure Start centre – one of Labour's bright ideas to nudge bad parents in the right direction.
It might well have worked if indeed any of those bad parents had been inclined to attend, but instead it was packed with conscientious mummies busy learning about breastfeeding, baby massage and tasty recipes for organic purees, while their babies played with educational toys.
All the mums who were more interested in the latest episode of Jeremy Kyle or where their next pack of fags was coming from stayed comfortably at home not troubling themselves with whether their baby would be better off with a bit more tummy time or if baby led weaning might be the way forward.
With the best will in the world preaching to poor parents simply won't get through. Even parents who have the best intentions can find such classes virtually useless.
I am the kind of mother who initially believed that the more information I could lap up about parenthood the better mother it would make me. But four children down the line I am not so sure.
When I was pregnant with my first son I went to every class on offer from tours around the hospital labour ward where I blanched as I handled the medieval looking forceps and quailed at the thought of that first meconium filled nappy.
I paid through the nose for NCT classes and sat in the teacher's chintzy living room with half a dozen nervous first time parents as she regaled us with the joys of natural births where contractions were wiped out by the power of aromatherapy oils and deep breathing.
I read every book I could find on the subject of parenting leaving me confused and conflicted – should I go for attachment parenting or opt for a rigid timetable of naps and feeds?
By David Cameron's reckoning this should have made me a model parent, but none of this prepared me for the reality of actually being a mother. It didn't take away the terror, the tedium or the sheer ignorance I felt when faced with caring for a newborn baby. In short all the knowledge in the world won't make you a great parent.
But what might have helped was a bit of practical assistance. Perhaps these feckless mums just give up because it is so very tough raising a child in this lonely, modern world where everyone is quick to tell you what to do, but slow to actually help you do it.
What might be of some use to all parents is, instead of the endless preaching and teaching, to offer us some practical help.
Grab back that £5million you are about to waste on pointless classes and instead invest it in a few more health visitors who might actually be able to spend a bit of time with new mums helping them to get the hang of breastfeeding and who could support them for long enough to show them what a vital role they play in their child's wellbeing.
If there is cash to spare it would be better spent giving working mums tax breaks on childcare instead of asking us to pay our taxes twice, once on our own salary and then again on our nursery fees, childminder or nanny's pay.
Encourage schools to offer proper, educational wrap around care, increase the allowance of state funded nursery hours.
That would have far more practical value to all parents, than any amount of preaching about parenting practice.
What do you think? Tired of parenting preaching? Would you welcome some practical help - above all tax breaks on childcare?