8 year old sleep issues

[Fairytalefancies]

Hi just looking for some advice.
My 8 year old DS has been very grumpy for...lets see.... probably a long time but more recently it has been at it's worst. Often it's during school time where I get this level of grumpiness and it is often when he has been struggling in school. He is behind in nearly all areas, mostly due to a lack of confidence in his abilities and other kids have ridiculed him when he has not understood something. Anyway recently he has been having great difficulty getting to sleep at night I wonder if it is anxiety about going back to school next week.
He generally resists going to bed at 8 pm - doesn't want to get his PJs on, brush his teeth or shower. He has a low lit lamp, music player for low level calming music if he wants it, dark room, comfy bed, he enjoys reading before bed so will do this, but he will not fall asleep and lately it been 10-11pm where he has finally gone to sleep!! Next day his behaviour is shocking he is grumpy to everyone, rude, argumentative and not fun to be around. Next week is school so we really need some tactics to try! He was upset this morning said he didn't want to tell me why but I managed to get out of him that he is sad about his nannies dying (2yrs ago but we recently visited granddad and he was reminded of nanny) and scared of killer clowns!
Any experience on this and advice is appreciated.

What time is he getting up in the morning at the moment, while being awake until 10-11pm?

Also, what happens between the 8pm bedtime and falling asleep?

I would start off getting him up at the time he needs to be up for school. Every day from now onwards. Up and starting the day - breakfast, get dressed, crack on starting the day by the time school would start. Then keep him busy and active for the day.

At bedtime, offer time checks and count downs. Set expectations: At 7.30 we are getting pjs on, teeth brushed. In shower by 7.40 and reading until 8pm. Time checks from 6pm ("bedtime starts in 1h30m at 7.30..."). Then 6.30 and 7pm. Limit screen use from 6.30pm

From going to bed (8pm) onwards you should expect him to stay in his room, lying on his bed doing nothing and being quiet. Bore him into going to sleep because there is no other option to do anything else.

I also find a household daily routine helps regulate the body clock so helps with bedtimes. Get up at the same time 7 days a week, breakfast at same time, dinner and tea all at a very regular, routined times of the day. These come together to help with a more structured and routined bedtime.