Six Flags Home School Day

From their website:
Six Flags hosts the 17th annual Home School Day event on August 27. Enjoy a fun filled day at the park with your family and friends. A special all-you-can-eat Home School Day picnic is also available in our private picnic grove. Contact SFGAMspecialevents@sixflags.com for additional information.

Make Six Flags Great America your outdoor learning lab. We offer teachers and students curriculum guides to make the day an educational experience. Learn More about our Educational Tools.

More details from a mailing I received:
When: Monday, August 27, 2012, 10-6 are the regular park hours. 6-8 is exclusive ride time for those that purchase the Home School Day ticket, good on certain rides. Hurricane Harbor is closed by this point in the season.
Where: Six Flags Great America
1 Great America Parkway
Gurnee, IL 60031
Located on I-94 at Route 132 (Grand Ave.)
Cost: Kids 2 and under are free.
Everyone else — $28 each with promocode HOMESCHOOL
Also, if you are coordinating for your group you can earn one free ticket per 20 purchased.
Parking — $20
Picnic Grove Meal — $11.50 each (available from 4-5pm
Processing Fee — $10
Tickets must be ordered in advance
If you have questions or need more info  call: 847-249-1952 or email SFGAMspecialevents@sixflags.com