The main problem that Victorian schools had to cope with was that of getting children to turn up for lessons. All school Log Books refer to the many reasons (or excuses !) for absent children.
Illness was a very common, and usually genuine, reason for staying away from school.
In country districts the older children were needed at various times of the year to help with haymaking, sheep-shearing, potato picking and other seasonal farming jobs. These often needed many hands, and many parents could not manage without help from their children.

This is a typical entry from the Log Book of Llanbedr National School from 1878 :
24th June - "School work again interrupted by non-attendance of all the elder children, who, notwithstanding the warnings of the Attendance Officer, are employed making hay".
Many schools had "Attendance Officers" who were supposed to make children go to school regularly, but very few of them were any good at the job.
There is another cause of missing school on the next page...

Getting paid for not going to school ! ...