The current yr11's are the first year that are requored to stay in some form of education until the age of 17. But that can be an apprenticeship or employment with trainingas well as school or college. I did hear that the following year, this would be extended to 18, but not 100% on that.
Circular is correct that the school leaving age is not changing. Young people have a choice of full time education or training, an apprenticeship or a paid job with training. Young people who have a "level 3" qualification (equivalent to two A-levels) are exempt from the requirement.
RPA - Raising the Participation Age RPA comes into effect from the last day of the academic year 2013. From Summer 2013, young people will be required to stay in education and training until the end of the academic year in which they turn 17. From Summer 2015 this will be until young people reach their 18th birthday. To access further information please click on the following link; www.thegrid.org.uk/learning/1419/participation/documents/rpa_raising_participation_age.pdf
OP there are no laws coming into force about leaving school - there are laws about staying in education until 18
Also colleges will be able to offer courses to teens from the age of 14 years - so from year 10 teens could choose to not continue with school and move to a college to do a more vocational course if that is what would suit them better