It is not surprising that parents were unhappy about letting their children go to school if there were any diseases in the district which could quickly spread through the whole school.
This comes from the official Log Book of Llanbedr National School for 1888 :

This Log Book entry reads :
21st March - "School closed for six weeks because of Diptheria. Three of the scholars died owing to it".
Diptheria was a particularly dangerous disease which caused the throat to swell up and block the airways to the lungs. It was one of several infectious illnesses which were common in Victorian times but are now very rare. The lack of money in many families meant that living conditions were often very bad and diets were poor.

Sadly, there are deaths from other causes reported in most early school Log Books...

Death of a young schoolgirl in 1883...