The First Minister said there was “more reason to be optimistic now than at any time since early autumn” and she was “considering if it might be possible to accelerate the exit from lockdown in any way”.
She also told MSPs that as a result of the success of the vaccination programme, the Scottish Government now aimed to get as many children back to school as possible from March 15.
Last week Ms Sturgeon, who was accused of failing to give people hope that lockdown would end soon, had said older primary pupils would be back in class, as well as secondary pupils studying for national qualifications, from March 15.
However, that has now been expanded to ensure all high school children could “spend some time in school” from that date, while after-school and breakfast clubs could also start up again.
Ms Sturgeon reiterated that all pupils will be back in school after the Easter holidays, unless there is new evidence to prevent the move.
Addressing MSPs in Holyrood, she said: “I have always said if we can go further and faster, then we will not hesitate to do so. All of us want to move on as quickly as possible – and, as a priority, to see friends and family again. I hope that day is now not too far away.
"The sacrifices we are all making are undoubtedly having an impact. Collectively, we are suppressing the virus, and saving lives – 657 new cases a day is the lowest level for five months – but it is still 13 times higher than the numbers in mid-August.
“To make sure we don’t see any reverse in our progress that would put that in jeopardy, it is really important that, for now, we all need to abide by the lockdown rules.”
The First Minister said consultation had taken place with Cosla and councils, the government’s Education Recovery Group, and the scientific advisory subgroup on education and children’s issues.
She said as a result, the return of children to school would happen faster.
Children in primaries one to three went back to school last week, as well as some senior secondary students who have a practical element to their courses, with Ms Sturgeon confirming that from March 15 “unless new evidence or new circumstances force us to reconsider” all children in primaries four seven will go back to school on a full-time basis.
"We will also take the next steps in a phased return to secondary school from March 15, with a clear expectation that all secondary school pupils will be back in school on a full time basis after the Easter holidays,” she said.
"However, it is the intention that all secondary school pupils will return to spend some time in school from March 15 until the Easter break.
“Students in the senior phase of secondary school – that is years four to six – who are taking national qualifications will have priority for face-to-face lessons in school. This will ensure that they can have their hard work fairly recognised, with qualifications under the Alternative Certification Model.
"Although years four to six may have priority, we expect that all children in secondary school will receive some in-school education each week. This will allow pupils to get used to being back in school and allow them to start seeing friends again. This is important for wellbeing as well as for education.”
Ruth Davidson, the Scottish Conservative leader at Holyrood, agreed the move would be “welcomed by pupils, parents and teachers who know there is no substitute for learning in a classroom”.
But she said Ms Sturgeon had performed a “U-turn” since her announcement on lockdown last week.
Ms Davidson said: "While today marks a gradual speeding up for a return to schools, the First Minister’s latest announcement was also typically vague and only prolongs uncertainty. No-one wants to risk an increase in cases by moving too quickly, but pupils deserve better than guesswork based on the SNP’s drip feeding of partial information."
Scottish Labour’s new education spokesperson, Councillor Michael Marra said the return of pupils was “a vital step towards the start of repairing the damage of the pandemic” but he said parents would have questions on the “part time arrangements”.
“Unfortunately, it follows the usual shambolic pattern of councils, who are responsible for actually running the schools, finding out at the same time as the whole country. Plans are not in place and no answers are available,” he said. “This is not a planned reopening. It is reactive and haphazard. Families and our teachers need to see a plan that is safe and structured.”
Ms Sturgeon stressed that two-metre distancing and mask-wearing was still vital in schools until Easter, and older pupils will be encouraged to take twice-weekly lateral flow tests, as will all school staff.
Scottish Liberal Democrat Willie Rennie asked how teachers could be expected to “juggle the workload” if “two thirds of the class are at home because of two metre physical distancing”?
Ms Sturgeon responded: "Teachers want children back in schools as quickly as possible. We have to do that in a phased way to make it safe and we listen very carefully to the views of teachers.”
Asked if school staff would be prioritised for vaccination by Scottish Greens MSP Alison Johnstone, who said some special school staff in the Lothians had been turned down for the jab, Ms Sturgeon said: “We are following the advice on the JCVI and that's the right thing to do as supplies for vaccines are still constrained to some extent.”