LilieKat do you have an autistic child? I only ask this because whilst training and clear explaination is invaluable to helping them Bible studies based on JW doctrine are both damaging and unnecessary. Quite honestly learning to cope with their peers and make sense of the world are more important lessons than religion. My son was 8 when we left no longer an infant. He was not badly behaved but the meetings were damaging on many levels, it wasn't just how long they were and the demands to pay attention and be quiet, it was the nature of the doctrine that was the issue.
Since children with ASD can fear unlikely events such as meteors falling from the sky etc some of the literature including My Book of Bible Stories plays on these fears. Some of those stories are truly barbaric. When we left we threw out all the societies books because the illustrations terrified my son and brought about incidents of hysteria at school.
My son has attended church services and particpated in school assemblies with no difficulty, The main difference has not been the length of time or solomn occasion but the tolerance and inclusion. He has not had nightmares over St Georges day parades or carol services or even easter assemblies. These occasions emphasised positive messages for him. Whilst he only attends occasionally when the scouts or school have an event he is comfortable to go and has not been taken out of the building to be disciplined.
It is the religion itself and its doctrine that are harmful for any child not just those with special needs.