Primary school teachers could be trained to demonstrate to children how to brush, the London Assembly’s health committee said.
Their report said: “Schools and early years staff will need training to deliver this, which could be done through working with NHS London to identify child oral health leads across each borough.”
More than a quarter of London children suffer tooth decay by the age of five — higher than the national average.
One million youngsters in the capital did not see a dentist last year despite care being free on the NHS.
Child dental health is uneven across London with just 14 per cent of five-year-olds suffering tooth decay in Bexley, against 40 per cent in Harrow.
The British Dental Association welcomed the report, Keeping The Tooth Fairy Away, saying there were “massive inequalities” between boroughs.
It issued an alert earlier this year after almost 3,500 London children, aged five and under, had rotten teeth taken out in hospital last year.
Almost 70 per cent of children in Hackney were missing out on free dental care, while 10 London boroughs saw a “marked deterioration in children’s outcomes” over two years.
Dr Len D’Cruz, an NHS dentist in Redbridge, said: “Children’s oral health has been slipping back across the capital... Mayor Sadiq Khan has made a commitment to make London the world’s healthiest city.
“He now has a clear blueprint to achieve that goal with our children’s teeth.”
A number of London schools have become “sugar-free” by banning sugary drinks and chocolate in packed lunches.
The committee said London schools should be sugar-free by 2022, every child should see a dentist by the age of one and the Mayor should appoint a specialist to work on children’s dental health.
Committee chairman Dr Onkar Sahota said: “Schools are the centre of a child’s education and a commitment to sugar-freedom would be revolutionary. Every child in London could have a sugar-free start in life — the health benefits would be enormous.
“The Mayor has the clout and the power to encourage families and schools to make sure London children see dentists as early as possible, be part of a supervised brushing scheme and keep sugar to a minimum.”
A spokesperson for the Mayor said: “It’s shocking there are such large variations in children’s health across the city, depending on where they live”, and added that through his new Healthy Early Years London programme nurseries, children’s centres, schools, playgroups and childminders will be given support to help infants and pre-school children learn to eat less sugar, brush their teeth properly and visit a dentist regularly.
The National Education Union said supervised brushing “will need careful thought as it would have to be fitted into the school day and closely supervised by non-teaching staff”/Evening standard