DS wanting an extra day off school

[Unintentionallycausingoffence]

DS is seven, he was refusing to go to school on a Wednesday, the staff can find nothing on that day that would upset or worry him. DF helped me take him yesterday so today he refused, two members of staff from DS school
came and picked him up
and he went. This is rare that they have staff available to do this. He moved from MS to SS September 2022, he loves schools is very settled, they have no issues of any significance or note and he is progressing very well. Does anyone else have this? or have any idea what causes it? He does have ASC

Could it be the effort of attending for 2 days leaves DS exhausted, physically &/or psychologically, and he needs a low stimulus, low demand day mid week?

I was wondering that. What could we or the school do, to help him possibly? He is doing very well learning wise since moving to SS but he does struggle with focusing