Those that exist might not stand up to professional peer-scrutiny. Nonetheless, anecdotal evidence of the value of these programs indicates that the benefits of these programs are considerable. All of these programs cost something, at least initially. Hypothetically, such a district has a great deal of flexibility within the constraints of its current budget and personnel ceilings to redesign time usage. But what is possible in theory is very difficult in practice.
Students are already in class.
They arrive every day. They have to be served. The community is familiar with the current school, its offerings and operations, and its schedule. Most appear to have planned and implemented their changes with the assistance of foundations or other outside support. Some schools sought other sources of funds.