I actually wouldn't be too quick to assume the teacher's going to be ineffective here. We tend to pore over every word and it's easy to interpret "have a word with" as something that won't make any difference, but I think that's premature. I'd give her a chance to deal with the situation, and escalate only if it doesn't help.
I also think there's a difference between saying that someone's asking for it - which the teacher doesn't say - and saying that they aren't helping the situation. If you are around people who like physically bullying you, it probably really isn't a good idea to start poking games with them! (Also, if you need support from teachers, it's a good idea to behave in lessons, although they, of course, ought to protect badly behaved children just as well as less well behaved ones. Still, if it were my DS, I'd be pointing out that teachers are more likely to believe that he was behaving well and the others were picking on him if the behaviour they see from him is consistently good than if it isn't.)
