It is geferlach whenever/wherever/whoever. It is a pritzas geder, a chink in the armor. If someones does text on Shabbos Chv"Sh, they are also letting others know, the recipients, and it a major chillul Hashem, pirsum hachet, it makes a chabura b'aveira. Busha
As was mentioned, it is IMHO2 a symptom, not the problem, which would be a lack of strong yiddish values.
It should be easy to check up your kids cell,