Mount St Bernard became an Abbey in 1848. Part of the Abbey was transformed into the Whitwick Reformatory, more properly known as Mount St Bernard Reformatory or the St Mary Agricultural Colony. It was opened in 1856 for `delinquent' Catholic boys and quickly became the largest in the country with up to 250 boys being held there. There were many riots and the boys often intruded on the monks peaceful way of life. As a result, in 1881 after sixty boys escaped, a decision was made to close the reformatory. It opened again briefly in 1884 when boys from the Liverpool reformatory destroyed the ship on which they lived and were sent to Whitwick while alternative accommodation in Liverpool was organised.The Juvenile Offenders Act of 1847 allowed children under the age of fourteen to be tried summarily before two magistrates, thus making the process of trial for children quicker and removing it from the public glare of the higher courts (the age limit was raised to sixteen in 1850). Then, between 1854 and 1857, a series of Reformatory and Industrial School Acts replaced prison with specific juvenile institutions. The Whitwick Reformatory (or St Bernard's Agricultural Colony as it was more correctly titled) was housed in old monastic buildings used by local Roman Catholics before the present abbey was built. Lay workers assisted the monks in supervising the boys. An average of 250 so-called delinquent boys from Roman Catholic families stayed there at any one time. There appear to be few contemporary records of the Reformatory. The Tate Gallery in London owns an oil painting by John Rogers Herbert titled " Laborare est orare" and is dated 1862. The artist described his work as: "LABORARE EST ORARE [to labour is to pray]. And some fell upon the rock: and as soon as it was sprung up it withered away because it had no moisture. And some fell among thorns, and the thorns growing up with it choked. And some fell upon good ground: and sprung up and yielded fruit a hundred fold. Gospel of St. Luke. The monks of St. Bernard's Abbey, Leicester, gathering the harvest of 1861. The boys in the adjoining field are from the Reformatory under the care of these Religious."
With such large numbers and lack of funds, and as many of the boys were already hardened criminals from the back streets of Liverpool, several riots and mutinies took place. In May 1863, eight constables from Loughborough stayed on the site for two weeks quelling a riot. A constable, PC Challenor of Shepshed was seriously injured. A year later, another riot took place and police from Loughborough, Shepshed and Leicester were drafted in to restore order. The Chief Constable of Leicestershire personally conducted the operation and the incident was the subject of a debate in the House of Commons. In 1868, sixty boys escaped. Many gave themselves up but eight were never found. A Home Office enquiry took place and found that that punishment within the reformatory was excessive, but the security was too lax. For several years, no further major incident occurred, mainly due to the strict management abilities of Supt T Carroll who was then in charge. However, in 1875, Ambrose Phillipps de Lisle persuaded Carroll to become a land agent and as a result he resigned his post. The situation in the reformatory rapidly deteriorated. In November 1875 the local police had to be called in again when more than fifty inmates attempted to abscond. Some escaped as far away as Market Harborough but all were eventually recaptured. Figures showed that half the boys returned to their criminal habits on release. On Sunday 27 July 1878 a fierce encounter took place between the police and a large number of the boys. After Mass it was the custom for the boys to assemble in the playground before entering the dining room for dinner. Only one attendant was on duty in the playground at the time. Having obtained some knives, some boys attacked the master and took the keys to the building. Some sixty boys escaped through the gates. Most of the boys came from the Manchester area, and the absconders attempted to return to that area by skirting the north of Loughborough, making for the swing bridge across the canal. Thus they made their way in a group for the Ashby Road, turned east along it towards Loughborough and then at Thorpe Acre junction turned north to avoid the centre of the town. The reformatory's certificate to operate was withdrawn in 1881 when there were 96 boys in residence. Their reputation was so bad that no other home could be found for them, and eventually they were discharged. The Reformatory was re-opened in 1884/5 to take boys from the Liverpool Reformatory. These boys had mutinied, burned and sunk their own reformatory, which was a former battleship (The `Clarence', moored in the Mersey). The Admiralty donated another ship, which was again sunk just four years later. On this occasion the Whitwick premises were considered too dilapidated to be used again and the boys were sent elsewhere. Local historians cite a claim that many boys died of typhoid at the reformatory and that a wooden cross, still standing, marks the site of their graves.