Speaking at a Scottish government coronavirus briefing, the first minister said the decision has been taken following an assessment of relevant data.
"When the Easter holidays end, virtually all pupils will return to school full-time, so secondary schools will go back to in-person, full-time learning," Ms Sturgeon said.
She said the exception to this is children who are shielding, who are asked to remain at home until 26 April.
Ms Sturgeon added: "This, I know, will be a huge relief to many children and young people and of course to many parents and carers…"
The first minister also confirmed every person in Scotland will be able to get tested for COVID-19 twice a week.
The programme mirrors a similar initiative in England.
"This testing will be in addition to and will supplement the additional testing routes that are in place in priority areas."
She added: "This more universal approach to asymptomatic testing will allow us to assess the impact that might have on further suppressing transmission."
The system will use lateral flow tests and more detail will be provided by the Scottish government later this week, Ms Sturgeon said.
She added confirmation on further lockdown changes planned for 26 April, such as the opening of hospitality and more retail businesses, would be announced on 20 April.
Ms Sturgeon said the coronavirus is "down...but not out" in Scotland, and warned there is still a risk of spikes in cases as are being seen in other countries.
By 7.30am on Tuesday 2,577,816 people in Scotland had received the first dose of a COVID-19 vaccination and 463,780 their second dose.
The first batch of newly approved Moderna vaccines arrived in Scotland on Monday. It is due to receive more than one million of the 17 million doses ordered by the UK.