The Department of Education claims otherwise, but its calculations are based on at least one pretty bizarre assumption.
Per the DOE's Educational Impact Statement and Building Utilization Plan (both of which you can download here), the reallocation of classrooms to the charter school would actually make for a more "efficient" use of the building.
(The EIS does acknowledge that "some [extracurricular] activities may need to share classroom space or the scheduling of these activities may change as a result of greater demands on the available space during or after school hours.")
There are some issues here—more "efficient" use of the classroom space may just be code for either larger class sizes or too few classrooms, especially for special-needs and ELL students (of whom the Community Roots charter appears to enroll a negligible amount, natch). But the biggest headache comes down the road, when the DOE—which aims to push the combined student body past the school's target capacity with the assumption that they can efficiently sardine in more kids—has to allocate space based on its own projections. Which are a joke.
The Community Roots Charter will apparently hold steady at 50 students per grade, eventually bringing a total of 150 extra kids to the building. Projected enrollment for the special-needs school assumes current numbers will hold steady. PS 67 is a "zoned school," bound to serve any student in the district who doesn't enroll elsewhere; in the Impact Statement, the DOE projects its future enrollment using this graph:
So, it so happens that this year's kindergarten is the smallest grade in the school. It's reasonable to assume that 27 kindergarteners this year means 25-30 first graders next year—but how, aside from wishful thinking, do we treat this number as anything but a blip?
By 2013-2014, when the charter is anticipated to be a fully functioning K-8 serving 450 students, the DOE's Building Utilization Plan (which makes slightly more conservative projections) suggests how every single one of the building's classrooms will be full; it's based on the assumption that PS 67 will have no more students than it does now, and possible more than 10% fewer.
Please tell me there are some sophisticated demographic calculations out there to explain how the K-5 population of Fort Greene (Fort Greene!) really is going to decline in each of the next three years. (Maybe they'll all go to charter schools?) It looks like the Bloomberg administration's blind allegiance to charter schools is playing hell with their math skills.