An inspector visited Craneswater Junior School in March and praised its quality of teaching and the behaviour of pupils.
Headteacher David Jones, who has held the role for 13 years, said that the whole school was ‘pleased’ with the report.
He said: ‘The rating reflects the hard work all the staff have put in and the really good behaviour of our pupils.
‘It is a real pleasure to work here. This is a community school and the children here are fantastic.
‘They are happy here and in many ways that is the most important thing.’
In her letter to the school, inspector Catherine Old said Mr Jones had ‘built a team of dedicated teachers and leaders’ and that the school had a ‘friendly and welcoming community atmosphere.’
She added: ‘Several parents were keen to tell me how well their children settle at your school, particularly those who join from outside Portsmouth.
‘The inclusive culture of your school is best exemplified by the weekly singing assembly, where all pupils and teachers sing the school song joyfully together.’
In its last inspection in 2013, Craneswater was rated ‘good’.
But it was asked to improve the quality of writing for pupils who have special needs or disabilities.
Two more classrooms are set to be built on the school site, which would allow it to expand pupil numbers from about 410 to 480.
Mr Jones said: ‘The inspector was very impressed with pupil behaviour and we are very proud of that.
‘She recognised that we have done a lot of work to improve the quality of writing.
‘The teachers here work a huge amount of hours.
‘It’s not a job where things can just tick over.’
He added: ‘I spoke to the children as well after we got the report and said they should be really proud of themselves.
‘I know you can never stand still though and we will continue to improve and develop our staff.’