Free school meals for children in P4 will start in the new school year but P5 pupils will have to wait until January, the Scottish government has announced.
Currently all P1 and P3 pupils in Scotland are entitled to free school lunches.
By the time P5 children are offered the meals in January, about 90,000 children will be eligible.
Similar support will be offered to low-income households during the holidays.
The Scottish government said its commitment to roll out universal free school meals to all pupils, including P6 and P7, will happen by August next year.
Education Secretary Shirley-Anne Somerville said: "Free school meals are a vital support to thousands of children and young people across the country - ensuring that children have access to a free, healthy and nutritious meal every day they are in school and are ready to engage in learning. "
The cost of the pledge for the 2021/22 term is expected to be £28m.
A further £21.75m is also being provided for "targeted free school meal support" during the school holidays in 2021-22.
This will start in July and be available for about 145,000 primary and secondary children from low-income households.
It will be up to individual councils to decide what approach they take in school holidays - and this may include the provision of direct payments, vouchers or food parcels.
Stephen McCabe, of local council umbrella body Cosla, said: "Councils across Scotland have long been committed to delivering healthy free school meals to eligible children and young people.
"We are pleased that, in partnership with Scottish government, this commitment can be further expanded."
The Scottish Conservatives announced a similar policy idea before the SNP's plan was announced last year.
The Scottish Greens argue that free school meals should be provided in high schools as well as primary schools.