Schools are following Tesco's example and taking a stand against parents who turn up at the gates wearingpyjamas.
They are chastising parents for dropping children off - and collecting them in the afternoon - without first changing out of their nightwear and slippers.
One head has written to parents warning that their failure to get dressed for the school run is 'slovenly and rude'.
Parents are being urged to dress appropriately when dropping their children off at school (file photo)
He took action after up to 50 mothers a day began arriving in the mornings wearing pyjamas and slippers.
The moves comes after a Tesco store in Cardiff took the unprecedented step of banning customers from shopping in their nightwear.
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Staff at the branch imposed a dress code after noticing that large numbers of women were walking down the aisles in dressing gowns, pyjamas and slippers.
A notice at the entrance to the store now reads: 'To avoid causing offence or embarrassment to others we ask that our customers are appropriately dressed when visiting our store (footwear must be worn at all times and no nightwear is permitted.'
Mother-of-two Elaine Carmody, 24, was one of the first to be marched out of Tesco by a security guard for wearing her pyjamas in store.
She said: 'I just don't understand it. I go in other shops in my pyjamas and they don't say anything.
Unwelcome: Elaine Carmody was asked to leave a Tesco store in Cardiff because she was wearing pyjamas
Now it has emerged that many teachers are behind the store's stance.
Head teacher Joe McGuinness became so fed up with PJ-clad mothers turning up at his primary school he sent a special bulletin home with the children.
Wearing pyjamas and slippers when dropping off their children at school was 'slovenly and rude', he said.
He wrote: 'Over recent months the number of adults leaving children at school or collecting children from school dressed in pyjamas has risen considerably.
'While it is not my position to insist on what people wear, or don't, I feel that arriving at the school in pyjamas is disrespectful to the school and a bad example to set to children.'
Defending his stance, he said: 'There used to be about 15 to 20 pyjama-wearing parents, but there is anything up to 50 now.
'People don't go to see a solicitor, bank manager or doctor dressed in pyjamas, so why do they think it's okay to drop their children off at school dressed like that?'
Mr McGuinness said EU law prevented him from banning mothers from wearing pyjamas to his school, St Matthew's Primary in Belfast.
But he said there had been no complaints since he sent the letters home several months ago.
Most teachers who contributed to an online discussion about nightwear on the school run were strongly in favour of a tougher line against PJ-wearing parents.
'They are indecent slobs with no respect for themselves or others. It should be illegal to dress that way,' one wrote on the Times Educational Supplement online forum (pls keep).
Another said: 'I wonder what those slobs in pyjamas would say if they were to enter the classroom only to find their children's teachers there, dressed in their pyjamas.'
One said parents who wore nightwear to school marked themselves out as 'Jeremy Kyle' watchers.
The teacher commented: 'I don't find it particularly offensive to see parents at the school gate in PJs, and we have plenty of them where I work.
'I do admit that I mentally categorise the repeat offenders as Jeremy Kyle-watching sofa-hoggers, but at least they have bothered to bring their children to school/collect them on time.'
Five per cent of parents have driven their children to school wearing
