I see there is no mention in the report of the criteria for referral, so it's just that the number of referrals has gone up. This could be because the criteria are much more general than they were originally, or because the people doing the referring are more sensitive (read over cautious) about things. The fact that the number of referrals is rising does not, of itself, mean that more children are at risk or are being radicalised.
When my wife was at primary school (in the 1960's), her parents were called in to discuss a "problem", namely that my wife was writing stories about death and war and producing drawings related to those subjects. What the school didn't know was that on one visit to Poland, my wife had been taken to visit Auschwitz with her parents and that it was normal for her parents friends to come round for dinner at weekends ... where discussion about the things which had happened to them during the war was common.
I wouldn't be in the least bit surprised to find that in all Muslim families there are discussions about what is going on in Syria, Iraq and other places, and about their worries about IS and teenagers being radicalised. So it is hardly surprising that some of the younger ones pick up on this and may come out with it at school ... and be referred as a result.