its largest UK factory in Lowestoft, where all its meat products and frozen vegetables are processed. Huntley & Palmers biscuit company has a base in Sudbury. The UK horse racing industry is based in Newmarket. There are two USAF bases in the west of the county close to the A11. Sizewell B nuclear power station is at Sizewell on the coast near Leiston. Bernard Matthews Farms have some processing units in the county, specifically Holton. Southwold is the home of Adnams Brewery. The Port of Felixstowe is the largest container port in the United Kingdom. Other ports are at Lowestoft and Ipswich, run by Associated British Ports. BT has its main research and development facility at Martlesham Heath. Below is a chart of regional gross value added of Suffolk at current basic prices published by Office for National Statistics with figures in millions of British Pounds Sterling. Education Primary, secondary and further education Suffolk has a comprehensive education system with fourteen independent schools. Unusually for the UK, some of Suffolk had a 3-tier school system in place with primary schools (ages 5–9), middle schools (ages 9–13) and upper schools (ages 13–16). However, a 2006 Suffolk County Council study concluded that Suffolk should move to the 2-tier school system used in the majority of the UK. For the purpose of conversion to 2-tier, the 3-tier system was divided into 4 geographical area groupings and corresponding phases. The first phase was the conversion of schools in Lowestoft and Haverhill in 2011, followed by schools in north and west Suffolk in 2012. The remainder of the changeovers to 2-tier took place from 2013, for those schools that stayed within Local government control, and did not become Academies and/or free schools. The majority of schools thus now (2019) operate the more common primary to high school (11–16). Many of the county's upper schools have a sixth form and most further education colleges in the county offer A-level courses. In terms of school population, Suffolk's individual schools are large with the Ipswich district with the largest school population and Forest Heath the smallest, with just two schools. In 2013, a letter said that "...nearly a fifth of the schools inspected were judged inadequate. This is unacceptable and now means that Suffolk has a higher proportion of pupils educated in inadequate schools than both the regional and national averages." The Royal Hospital School near Ipswich is