While there's some skepticism in the thread, I'm not particularly surprised if this is true. Children who can get human tutoring do a lot better. An LLM that can answer questions and patiently explain likely offers some benefit.
What creeps me out about bringing LLM into early education is that it's a period where kids learn to socialize and cope with problems, and I do worry about forming substitute relationships with chatbots that are engineered for sycophancy / enablement. But I guess that's a problem either way, because almost every student will try an LLM at some point.