My kid's preschool loved having me bring chicks. I went there three times, so they could see the changes in the development as the chicks grew their feathers. Everyone had to be quiet and could come up one at a time and pet with one finger as I held each chik, and I brought a heating disc and plenty of chicks on a warm day so they wouldn't get too cold.
The first trip they were about 2 weeks old. A little young, but I trusted they'd be ok and they were.
I returned when they were about 6 weeks old. They could see the baby coloring and feathers, and see the combs start to grow. I brought maybe 12 of them.
I returned lastly at the end of their school year, and the chicks had grown a lot and looked like real chickens. I only brought a couple of them, because it was totally unnecessary to bring 20 full grown chickens at that point!!
This was at a private school.
Daughter is now in public school (second grade, soon third grade), and I asked if we could do this again for her class when she was in kindergarten. i was sad that the teacher, after checking with the principle and school board, told me health regulations forbid people bringing any animals except service animals, into school or on school property due to allergy concerns. I didn't pursue it any further, but was not impressed. There is so much one can learn from many animals, chickens included. Even after having chickens for 7 years or so, I am still learning amazing things about them!
And they didn't believe me when I told them these were special human-assistance chickens. They are "Danger-Sensing" chickens, so I know when it's time to engage stress-reduction skills.
Have fun taking your chickens in and showing them off! The kids will never forget them or you!