DD much preferred ORT in infants. Nowadays (yr 4) some of the Ginn are quite good...I( think her current ones are ginn level 9 ), themes like Dinosaurs which have factual sections, some fiction and poems.
( I do rather miss Floppy though )
Mention it to the teacher - reading boring books is demotivating. If there is some good reason why the teacher wants him to do the Ginn, then it'll help you to know the rationale.
I think a mixture of reading schemes is good. Our school explained that when students transfer to us from a school where only one scheme is used the children are sometimes flummoxed by different sentence construction/names/grammar. We use Ginn in conjunction with ORT and another scheme, and it seems to work well. But if DS is really bored maybe the level they have chosen is wrong?