Is it illegal for teachers to send text messages during evening self-study?

Violation. According to the relevant information, the school will stipulate that teachers should not use electronic devices such as mobile phones in formal education and teaching activities such as classroom teaching, collective lesson preparation, teaching and research activities, so as not to affect the teaching order and teaching effect. If teachers send information about teaching or student management during evening self-study, it may be considered as a reasonable work exchange and not illegal. However, if it is a private chat, entertainment and other non-work-related behavior, it may be considered illegal.