From US Lawshield:
CAN I CARRY MY FIREARM DURING PICK UP AND DROP OFF?
It’s that time of year again when students are returning back to school. If you’re a parent who drives your child to school, can you legally possess your gun while doing so? If you have a concealed carry permit, you are allowed to have a gun on educational property, but only for the purposes of dropping a student off or picking them up at the end of the day. While on educational property, the permit holder must keep their car doors locked at all times, unlocking them only to let the child exit the car or re-enter the car at the end of the day. Other than that, there are very few and very limited circumstances where a person can possess a gun on educational property.
In or out of carpool lines doesn’t matter. What matters is that you remain in the locked car and it’s only unlocke & open long enough to pick up the passenger.