Estyn report says girls outperform boys in maths
The performance gap in maths between boys and girls aged 11-14 has widened, according to education watchdog Estyn.
Overall, inspectors say teaching assessments for the Key Stage 3 students have improved since 2010.
As well as the gender gap, pupils on free school meals are not performing as well in the subject.
Chief inspector Ann Keane said: "Mathematical knowledge, understanding and skills are increasingly important for everyday life."
The Estyn boss added: "It is crucial that pupils develop a secure grasp of mathematics during their school years."
Teaching was good or better in the majority of schools visited and inspectors found that many pupils have a positive attitude towards learning maths.
Schools highlighted for best practice were Cardiff High School, Cwmtawe Community School, Neath Port Talbot, Caerleon Comprehensive School in Newport, and Cardinal Newman RC Comprehensive School in Rhondda Cynon Taf.
However, some schools still have a shortage of suitably qualified and experienced teachers which restricts their ability to deliver the maths curriculum successfully, the report found.