Education Scotland's team of inspectors is "now confident" Perth Grammar School has "the capacity to continue to improve".
The inspectorate will make no further inspections following a poor inspection report published in January 2020.
Councillors this week praised the improvement that has been made in the school to turn things around.
In January 2020 Perth Grammar was rated as "weak" in raising attainment and achievement and "satisfactory" in learning, teaching and assessment.
Perth and Kinross Council's Executive Sub-Committee of the Learning and Families Committee discussed the improvements made at the Perth secondary school when it met on Monday, March 20.
Headteacher Fiona Robertson has been providing regular updates to the committee on the progress being made and a council report was put before the committee on Monday.
Councillors were told senior education officers had visited the school on several occasions and met with staff and pupils "to support and challenge colleagues in raising attainment and achievement".
The report concluded: "The school’s ambition agenda sets out unambiguously an agreed approach to improve outcomes for young people so that all staff, and groups of staff, are clear on their individual and collective roles and responsibilities. Perth Grammar has made significant improvements in all areas identified in the original inspection of November 2019, and we will continue to monitor progress through local quality assurance processes."
Perth City Centre councillor Chris Ahern was delighted with the progress made.
Bailie Chris Ahern said: "All three of my children went through Perth Grammar. I have a great affinity with the school.
"I'm delighted to see the improvement made by not only Fiona and the staff but the pupils as well.
"The senior pupil leadership team have done some excellent work to improve the school not more so than in the house system. They've worked alongside the parent council in making it more visible.
"The outreach programme is excellent. That is working with some of the most challenging pupils in the area - completely disengaged with the education system - and I've seen them in that small environment in the community centre in North Muirton and it really is working. They are starting to get back engaged again."
Bailie Ahern said he was "very disappointed" in 2020 when he saw the report but to see the "massive improvement that has been done" he said was "a fantastic achievement".
Conservative councillor Caroline Shiers praised the improvement made amidst the "perfect storm" of the pandemic and a high staff turnover. She asked about what impact pupils having a pupil care and welfare officer was having on attendance and punctuality.
Headteacher Fiona Robertson said: "Our young people know exactly who to go to and it can be absolutely anything in terms of welfare including uniform too.
"The best parental engagement we've seen has been during the pandemic and since which I think is down to some innovative ideas.
"For example the police officers do 'Tea with a Cop' and one of the officers by chance once suggested to me 'Why don't you do Tea with the Headteacher?'"
"And therein lasts a very lasting experience we've had in being able to amend that to - and you can see a theme here - 'Tea with the Principal Teacher'."
Perth and Kinross Council will continue to monitor progress through local quality assurance processes.
