D.W.'s Blankie: Car wash dryers are not vacuums. They blow water off of cars.
Out of all the easy subjects that substitute teacher Miss Ratburn does with her brother's 3rd grade class, one of them includes the 1 X's table. Kids are not introduced to multiplication and/or division until this grade that Arthur and his classmates are in.
In "Arthur's Substitute Teacher Trouble" Prunella is in the grade above Arthur. In all other episodes, they are both in grade 3.