A school in Redbourn has been told it requires improvement after its most recent Ofsted inspection.
Redbourn Junior School, for students aged seven to 11, slipped from its previous Outstanding rating when it was visited by inspectors in June.
During the visit, the school’s inspectorate visited 17 classes jointly with the headteacher.
Inspectors noted "inconsistencies" in the quality of teaching at the school, meaning pupils are not making the progress they should - especially in mathematics.
School performance data, the work in pupils’ books and observations of pupils’ learning showed that teaching is "not strong enough" in some classes to ensure rapid and sustained progress across the school.
The vice chair of governors Lucy Eckley said an action plan is being drawn up to address the issues identified, which in many areas the school had already auctioned.
She said: "The key area which Ofsted have asked the school leaders to focus on is that teaching performance targets should place greater emphasis on pupil progress so this will be an ongoing focus in the coming academic year but we have already made clear improvements in the quality of teaching over the past year and the excellent SATS results the school received in July provides strong evidence of our high standards."
During the past three years there have been a significant number of staff changes at the school and of periods of absence due to illness within the leadership team.
The school, which teaches 243 pupils, was told teaching is not consistently good because not all teachers have persistently high expectations of what pupils can achieve as they move through the school.
Ms Eckley added: "Since our last inspection in 2008 Ofsted have been very happy with the school's performance and standards and in 2014 we were scheduled for an inspection as per their standard procedure.
"Redbourn Juniors is a happy, popular school that believes in the all round development of children across all levels of ability. It is also remains a high attaining school with SATs results this year higher than at any time since the school's previous inspection.
"The inspectors had many positive things to say about the school acknowledging that we are a high attaining school where achievement and behaviour are good; that we strive to develop well rounded and socially able children and provide a stimulating and imaginative curriculum which offers effective learning opportunities for all groups of children."
Inspectors praised the behaviour of pupils is good, and said attendance is now average.
Music, information and communication technology (ICT) and physical education were deemed to be the main strengths of the school.
The school will have a new executive headteacher from September. Ian Pattrick from Crabtree School in Harpenden will act as head until a new one is found.