When a Sim leaves to actively attend school, there is a random chance that they’ll be sent to another lot on a field trip. There are also plans for introduction days like with Elementary School, but the exact details of them haven’t been decided yet. The exact goals haven’t been decided yet, though most will involve skill building. The High School is still being planned and the details of it haven’t been locked yet, but much like Elementary School, your Sim will be assigned a series of goals. That’s not all, though! It’s not as simple as going through the same process every Sim day: the mod features introduction days, field trips, a variety of events, and for the more mischievous Sims, even the ability to play Hookie while a (off-screen) hologram does the work! Your Sim will then be assigned goals to complete, same as with open careers, which will determine performance. Much like the open careers in Get to Work, when it is time for your Child or Teen Sim to go to school, you will be asked whether or not you want to follow them, and if you opt to follow them, you’ll be taken to the appropriate venue. You can download an existing school from the gallery, or create your own, in any location in the existing worlds. The mod contains two new venue types: Elementary School and High School. 'If you have both The Sims 4 and The Sims 4 Get to Work Expansion Pack, The Sims 4 Go to School Mod Pack allows you to follow your Child and Teen Sims to school.

Zerbu has announced to the Sims Community readers that The Sims 4 Go to School Mod Pack is currently in development.Here what he said in his post:

Sims 4 mods go to school