The aspiring deputy leader wants private schools to do more to justify their tax breaks. "It's not enough just to lend their playing fields," he said. "They should open up their science labs, lend teachers to the state sector, sponsor academies and form trusts."
But the pronouncement has irked state school staff. "Private schools have a huge amount to learn from state schools," sniffed a spokeswoman for the NUT.
Independent sector heads accused Mr Johnson of playing at "the politics of envy".
As the creation of a new government in Wales takes yet more twists this week, speculation has it that "today is the day" for a new dawn in Welsh politics, whether it be set with a rainbow or not. The knives have been out for First Minister Rhodri Morgan all week but he is expected to announce his new cabinet.
Jane Davidson has been keeping a low profile. Her plans to revolutionise Welsh education with never-ending initiatives were on hold as the minority government did its best to salvage support from the opposition.
Dyslexic children have been dismissed as "lazy, thick or stupid" by Julian Elliott, an educational psychologist who has accused middle-class parents of using the diagnosis as a fig leaf for their children's inadequacies.
Another psychologist criticised pushier parents for buying Ritalin, a drug used to treat hyperactivity, to pep up their children's performance during exam time.
But it seems in Wales that the answer to some of the challenging children may be to tire them out in the great outdoors. Forest schools are the future, according to the Forestry Commission, which investigated the effects on children at a primary already converted to the Scandinavian ideal. Hopefully, the new education, lifelong learning and skills minister will agree.