Do the high school poll workers have to work at the polling place where their parents vote?

Yes.  High school election inspectors have different requirements than regular election inspectors.  Wisconsin §7.30(2)(am) requires that a high school election inspector work at the polling place serving the pupil's residence.  A high school student may assist at another polling place in their municipality, but cannot be an election inspector or perform any duties normally assigned to election inspectors.

Do high school poll workers get paid?

Yes.  A high school student serving as an election inspector may be paid or may volunteer their time.  A recent change in state law permits any individual serving as an election inspector to choose to work without compensation.  A high school student may want to work without pay as part of a community service requirement.  The amount of compensation is determined by the municipality.