Leighton-Linslade's Greenleas School has been downgraded to Requires Improvement after it was ranked by Ofsted for the first time in 14 years.
The previously Outstanding school was exempt from scrutiny until now, and was visited by inspectors on September 28 and 29, with its last inspection in 2007.
The school was declared 'Good' in Behaviour and Attitudes and Personal Development, but was ranked as 'Requires Improvement' for The Quality of Education, Leadership and Management, and Early Years Provision.
However, headteacher Rebecca Clarke stated that the school was "fully committed to addressing the issues" and thanked parents and carers for their "wonderful" messages of support.
Detailing areas for improvement, the report stated: "Teachers do not follow a single approach for teaching phonics to teach young pupils to read. There is too much variability in how effectively phonics is taught.
"Leaders should adopt a single phonics programme and ensure that the books that early readers are given to read are well-matched to their phonics knowledge.
"Pupils are not building on their learning and deepening knowledge in all subjects as well as they could. Leaders should ensure that all curriculum leaders have the training, support and knowledge they need to design a high-quality curriculum."
However, the report also highlighted areas in which the school was doing well.
It stated: "Pupils enjoy attending Greenleas School. They feel happy, safe and cared for. Staff know pupils and families well. All members of the school community feel part of the ‘Greenleas family’."
It noted that pupils developed "positive relationships", "had a good understanding of the school’s values", and were "keen to learn".
Its attitude to SEND was also praised: "Staff know the individual needs of pupils with special educational needs and/or disabilities (SEND). Pupils with SEND access the full curriculum. They develop greater independence and confidence in learning."
Since its previous inspection, the Derwent Road school has "expanded in size considerably" and opened a separate site at Kestrel Way in 2013.
The headteacher works over both sites, and there is a deputy headteacher at each site.
Due to its impressive rating in 2007 it was exempt from further Ofsted monitoring.
However, the controversial exemption system has now been axed and previously Outstanding schools are facing compulsory routine visits again.
A Greenleas School spokeswoman, said: "Alongside the many restrictions imposed on schools during the COVID pandemic, routine Ofsted inspections were suspended during the lockdown periods, and until the end of the Summer 2021.
"It was recently reported that Amanda Spielman, Chief HMI, was expecting half of the country’s Ofsted outstanding schools to be downgraded when the inspection regime restarted in September 2021.
"Greenleas was the first lower school in Leighton Buzzard to receive a visit from Ofsted since inspections restarted in the aftermath of COVID restrictions and formerly exempt from inspection due to its outstanding judgement.
"The school received a downgrading to a Requires Improvement judgement pursuant to the visit which took place over two days in late September."
Headteacher Rebecca Clarke stated: "The school is fully committed to addressing the issues identified by the inspection team which need improving.
"Work on these areas was already underway, but progress had been compromised by the competing demands of the pandemic.
"Streaming live lessons, prioritising curriculum delivery to address gaps in learning and supporting the children’s mental health had to take precedence over updating curriculum paperwork."
She added: “It is of course vital that standards in schools are protected, and it is Ofsted’s role to do this. However, it is unfortunate that an opportunity has been missed to celebrate the hard work and dedication of schools across the country to support children and their families during one of the most turbulent periods in living history.
"I am tremendously proud of my staff and how they have kept children learning despite the many challenges, and our parent view survey confirms that our families feel the same way.
“Myself, the governors and all the staff at Greenleas were overwhelmed by the wonderful messages of support we received from parents and carers when we advised them of the outcome. It was heartwarming to know we are supported by the wider Greenleas family.”
To view the report, visit: https://files.ofsted.gov.uk/v1/file/50172716