Also, we might want to cross-refer from what Tremenheere says here to other knowledge. Historians of education know well that one of the main reasons why children were not always at school, in the last quarter of the 19th century, was because their parents wanted them to be at work during periods of particular pressure.
This was especially true in rural areas during harvest time in the late summer or in the potato picking season during the autumn. In late 19th century, many poor people still depended on a genuinely family income and not just on the wages of the head of the household. Why does Tremenheere show no apparent awareness of this important issue when he discusses 'the chief causes of absenteeism'?
Is he perhaps not quite as objective and well informed as he might be? This all shows how critically the historian has to approach all source materials - it is only when there is a good body of corroborating evidence that one can be sure of historical facts.