The Simpsons (1989): Season 14, Episode 3

14 - 3: Bart vs. Lisa vs. 3rd Grade

After testing, Lisa is moved up a grade and Bart is held back so they are both in the 3rd grade together. The teacher thinks Bart is the smarter of the two since he already knows everything. They go on a field trip to Capital City and get left behind and lost. Blackboard 'Fish do not like Coffee'.