If you're not interested in straining your eyes to read that, I've transcribed it here:
Dear Mr. Jackson,
Thanks for rescuing the deer. It was really nice. I hope the deer find a new, good, home. I will retell this story this story to my class. You are a great helper. I think your really friendly. I was unhappy when I heard that the deer were going to get shot. I liked the deer a lot. You had to be careful to not startle them. Maybe you could come over some day. I would love to hear about all the animals youv'e seen. You did a really good job of how you handled the deer. I'm happy we didn't have to shoot them. Thanks!
Sonia [the "i" is dotted with a heart]
While it's not nearly as funny as the note Katy found on the beach, you still have to admire this young animal lover. She should be careful about inviting over strange men to her house, however. Just because he won't shoot deer doesn't mean he won't molest children. If Mr. Jackson is, as requested, entertaining you with stories of all the animals he's seen and stops to mention that he's never seen a beaver before, then run, Sonia, run.