My kid is in high school, and they communicate about emergencies through text, email, and automated calls. There are lots of jobs, especially low-paying ones, that will not let you check your phone during your shift, and they’re certainly not going to be okay with you leaving early to go pick up your kid. If the choice is “leave to pick up kid (who you know is safe with teachers), get fired,” versus “leave kid (who you know is safe with teachers), keep job,” it’s pretty simple math.