* The specific disability: Some disabilities are transient or improve significantly with early intervention, while others are lifelong. A child with a speech delay might outgrow it, while a child with autism spectrum disorder may continue to need services.
* Intensity and quality of intervention: Effective early intervention significantly increases the chances of a child making progress and potentially losing eligibility.
* Definition of "qualifying": The criteria for qualifying for special education services can vary slightly between states and school districts. A child might still need support but no longer meet the strict criteria for a specific label.
* Age of the child at the initial diagnosis: Younger children may show more significant progress than older children, leading to a higher rate of loss of eligibility.
* Data collection methods: Studies on this topic may use different methodologies, affecting the results.
While research exists on preschoolers' progress in special education, pinpointing a single percentage for those no longer qualifying after two years is impossible without specifying the factors above. You'd need to look at specific studies focusing on particular disabilities and geographic areas. Even then, the findings would represent a snapshot in time and location, not a universal truth.