Serious concerns have been expressed about an increase in poor behaviour in primary schools after figures revealed permanent exclusions had more than doubled in a year.
Assembly government figures released this week showed that 31 pupils were permanently excluded from primary schools in Wales in 200910 - the highest number in four years and up from just 14 the previous year.
There was also an increase in the number of primary pupils excluded for up to five days, from 1,612 in 200809 to 1,735 in 200910 - the highest number in five years.
Professor Ken Reid, chairman of the groundbreaking National Behaviour and Attendance Review, said: "Things are going seriously wrong in our primary schools if these two sets of figures are anything to go by.
"Why should primary schools be finding it more necessary to exclude pupils? It's a worrying indication that things could get worse, because these behaviour and attendance problems are going to feed through to secondary schools."
Overall, the number of permanent exclusions in Wales has fallen to a new low of 185, down from 213 last year and a high of 465 in 200405, which education minister Leighton Andrews described as "encouraging".
But there is concern that a greater percentage of permanent and fixed-term exclusions in 200910 were for incidents of violence towards staff and pupils than the previous year.
Assault or violence toward staff and pupils counted for 30.5 per cent of permanent exclusions and 23.4 per cent of fixed-term exclusions (of up to five days) in 200809. But in 200910 those figures increased to 37.3 per cent and 25.5 per cent respectively.
The NBAR report recommended a "zero-tolerance" approach to classroom violence, and Professor Reid said he was "disappointed" that it appeared to be rising.
Anna Brychan, director of heads' union NAHT Cymru, said: "School leaders are finding that younger children are exhibiting more serious behavioural problems and may need intervention from services other than just schools.
"Equally there may be training issues for teachers and support staff in dealing with unacceptable behaviour and if training is an issue in this increase, we'd want that addressed urgently," she said.
As TES Cymru recently reported, some teachers in the play-led foundation phase for under-sevens have reported an increase in poor behaviour among a significant minority of pupils.
Professor Reid, the former deputy vice-chancellor of Swansea Metropolitan University, said primary heads are also encountering more pupils with serious psychological and mental health problems.
Teachers are finding it "extremely difficult" to cope, he said, and need more training and resources to help deal with challenging pupils.
Bullying or theft and possession and use of a weapon also accounted for a larger percentage of permanent exclusions, while substance misuse and racial or sexual harassment had fallen.
Education minister Leighton Andrews said: "We've made good progress but can't afford to be complacent when it comes to this important issue."
An Assembly government spokesman said: "Permanent exclusions from primary schools are very few in number and little can be read from a rise in one year, as this could be related to a very few random incidents in a few schools."
- Original headline: Permanent primary exclusions double in just one year