The country’s biggest academy sponsor has pulled out as the backer of two planned schools in the wake of concerns over standards. United Learning Trust has scrapped plans to sponsor schools in Oxford and Northamptonshire. The decision comes after ULT’s Sheffield Park Academy was criticised by Ofsted for making inadequate progress since being placed in special measures last September. Schools Secretary Ed Balls has described the situation there as “unacceptable” and has expressed “very serious concerns” to ULT.