Please find below data from the School Capacity Collection 2010 (national/LA and school level).
Download the Schools Capacity 2010 School Capacity Collection Metadata specification here (Word doc, 738KB)
Download the Statistical Release Report, Schools Capacity 2010 (pdf, 50KB)
This data is also available on the DfE website: http://www.education.gov.uk/rsgateway/DB/STR/d000982/index.shtml