[Ruffy]

I think a blend may be best.

Engaging with police/school(s)/parents as you see fit may be useful simply to get the situation logged so that when/if your grandson does get into a scuffle there is documented history to support his side of the story.

I agree with other comment that this is more than just bullying, it's probably harrasment/assault and theft so criminal reporting to the police is also an option.

However asserting himself is always a useful life lesson but, as I am sure you know already, you will need to be careful how you encourage your grandson if he is autustic spectrum. Appropriate coaching can be difficult to gauge. He may not fully comprehend how to control his response, or may simply be emotionally overwhelmed by the concept of engaging in conflict, which is possibly why he is more easily targeted in the first place. Further retaliation remains a risk that he will also need to be prepared for. Without knowing your grandson, I realise I can't comment much on how he might be able to deal with it.

I always asked my kids never to start a fight but I told them they would have my full backing to finish one by whatever means necessary if someone picked on them.

(Sorry if this sounds a bit preachy. I have a little experience to relate to here: My son has Asperger's (as do I, probably). I remember quite well the day the police came knocking at our door after he had defended himself and a friend by bloodying a harrassing bully's nose and the bully had gone crying foul to his own parents. It took a little explaining but it went no further and there was no repeat.)