I send DS1's back for swapping after he has read them once but he told me today that the TA said he should be reading them more than once. We don' do reading every day and it takes the teacher a couple of days to actually swap them so it basically works out as 2 new books a week (he gets 2 at a time).
He reads them through easily first time so I don't see the point of reading them again but am I missing something??