The most useful study of the five was also the most honest about its own limits. Ayman Shakeel ran a randomized controlled trial, posted to the EdWorkingPapers repository in late 2025, that followed 333 students in Grades 2 to 5 through a high-dosage literacy tutoring program (Shakeel, 2025). The headline result is a letdown. Across the whole group, the average effect on literacy was not statistically significant.
Stop there and tutoring looks like a failure. It is not. The breakdown flips the story. For the students who started furthest behind, the program produced a real gain, about 0.2 standard deviations. Stronger readers gained nothing. A few even slipped. So tutoring did not fail. It worked for the students who needed it and did little for the ones who did not, which is about what you would expect from help that is only as good as its aim. It is still a working paper, not peer reviewed yet, so treat the exact number as provisional. But the shape of it lines up with years of high-dosage tutoring research.