All schools in Kenya will remain closed until next January because of the coronavirus pandemic.
Final year exams, usually taken in October and November, have also been cancelled.
Education Minister George Magoha said students would repeat a year as schools had closed in mid-March, three months after the school calendar had begun.
But colleges and universities are to reopen in September if they abide by strict guidelines.
The East African country has confirmed more than 8,000 cases of coronavirus with at least 164 deaths - and there has been a recent surge in new infections.
On Monday, President Uhuru Kenyatta announced a phased reopening of the country, including the lifting of travel restrictions in the main cities of Nairobi and Mombasa.
However, he did extend a nationwide overnight curfew - from 21:00 to 04:00 local time - for a further 30 days.
Kenya's academic year runs from January to November.
"The 2020 school calendar year will be considered lost due to Covid-19 restrictions," Mr Magoha said.
This would apply to public and private schools, he said.
The government-run Kenya Institute of Curriculum Development has been providing school programmes via the radio, television and online since students stopped going to classes in March.
But while some have been able to cover the syllabus using these resources, there are many others who do not have access to the technology.
Mr Magoha said his ministry would explore how to make online learning accessible to all pupils.