The Residential Landlords Association (RLA) has warned that restrictions on the growth of shared housing are pushing up rents for students.Some local authorities with universities have decided to use planning powers known as Article 4 Directions to prevent the spread of shared housing.The RLA's annual UK-wide table of rents, Accommodation for Students, has revealed that the average weekly student rent bill has risen from £67.11 in 2011 to £68.70 in 2012 – an increase of 2.4%.Studen...