The career module contains settings to work-around the way that the Sims 4 core-script will assign career jobs to households marked “Played Households” if they are not the active household and employment ranges for each age-group. The ranges are set-up in a minimum/maximum manner. So, for Teenagers who, with EA’s defaults, have a range of 40/50. That means they will have no less than 40% employment and no more than 50%. If the numbers drop below that, Teenagers will be given jobs. If the number goes above 50%, they will quit their jobs.
In the Sim Flags menu, there is an option on Sims older than Teens to Freeze Career.