The only school-based programs I'm aware of are in specialized schools of various kinds, such as congregated GT schools and (in a slightly different, but still relevant, context) vocational and arts schools, which already have built-in immersive instructional time. Our vocational-technical school (which otherwise is not particularly out of the norm academically among its peer institutions) has had a few students whose deep dives in their voc area took them to the national level in in-field competitions. But in many voc programs, instruction turns out to be surprisingly routinely individualized and self-paced, with a fair amount of headroom for advanced learners.
