With population density being what it is in China and with school buildings being so big and with most people using Wechat (THE PARTY LINE), it makes sense to send a message instead of running all over some damn school building looking for people. Chinese lead staff meetings are without purpose anyway so the WeChat is nice.
Loads of directions and last minute messages are the price we pay for the modern technology nowadays. Scared we should be when the AI overwhelms our day to day lives one day. Do you have to have a smart phone to do your job today?