My mother had her own ideas about that.
It we just felt hot, she would measure:
Under 37.4 it was all ok. (unless dirty)
Between 37.5 and 38 she would check again 3 times that day until under 37.4.
Between 38 and 39 a 500mg paracetamol suppo and check again 3 times a day for at least 3 days until under 37.4.
39 or higher a 1000 mg paracetamol suppo and check again 3 times a day for at least a week. If not under 37.4 at the end of the week for another week.
If we complaint about a headache:
She would just measure a gave me 500 or 1000 paracetamol depending how much i would complain i think. Unless if the temperature was according the above.
If the thermometer came out dirty:
39 or higher she gave the 1000mg suppo first and about an hour later a ducolax or glycerin suppo until they worked.
between 37.5 and 39 ducolax or glyverin suppo first until they worked and 500 or 1000 paracetamol suppo after that.
37.4 or lower ducolax or glycerin directly until they worked and check again daily.