Can someone explain why do Japanese choose to use katakana sometimes when writing for Japanese people?

Went to Osaka and one street had a street painting that read “スクール　ソ”ーン”, meaning school zone, i mean I would understand the use of katakana if the word used doesn’t exist in Japan, but this was taken in the middle of nowhere.

My own hypothesis is that’s being used to get people’s attention, any other idea?

Thanks.