In 1876 the Mercy Sisters paid £14,000 for Claremount House and its 84 acre farm, the former home of the right honourable Denis Browne,the son of the second Earl of Altamont.
On Jan.1st 1877 the first four sisters arrived in Claremount by coach. The sisters set the land, grew fruit and vegetables which they sold and opened a bakery in an effort to make ends meet.
In 1878 they opened a school for the needy in a renovated farm building at the rear of the convent.
Also in 1878 the nucleus of what became St. Joseph's Rural Home Economics College began when the sisters held classes in cookery, laundry and sewing for the women of the area. Later Bee -Keeping classes and Poultry keeping classes were added. These classes developed into a residental training course for girls in cookery and Rural Domestic Economy. The school commenced with an enrolment of five pupils. Accomodation was provided for these pupils in the convent.
In 1880 a Pension School was opened, where better off families paid a fee. The 3R's were taught as well as music, french, drama and singing. In 1881 the school was placed under the National Board of Education. Fees were discontinued, salaries were paid and the old Pension School , consisting of renovated stables was now called the National School.
In 1906 a very limited number of students were admitted as boarders. In 1907 an extension of three classrooms was built at a cost of £60. Soon after the establishment of The Irish Free State in 1922, the Department of Education and Science was set up and schools were invited to draw up an alternative programme for Senior students. This was the beginning of the system of "Secondary Top" and from 1924 - 1940 the senior section of the Convent National School operated as a "Secondary Top". The school continued to operate as a "Secondary Top" until the secondary school was opened in 1940. Sr. Paul Moylan was appointed principal. All subjects were taught through Irish. The boarders were housed in the convent.
An extension in 1942 to the Domestic Economy School made provision for an extra 30 pupils.
Many students qualified as Poultry Instructresses. With the advent of free education the numbers began to grow rapidly and additional classrooms were added. In 1976 a new canteen was built by the sisters. In 1976/'77 an annex to the canteen was built - "The Transition Year Flat". This building marked the introduction of the transition year option into the curriculum of the school. The cost of this was again funded by the sisters as no government grant was available.
In 1978 the sisters once again agreed to fund a new staff room and cloakrooms and as it became increasingly obvious that leisure facilities were grossly inadequate the sisters once again agreed to fund new tennis, basketball and hockey courts.
In 1984 the R.H.E school was closed and rooms were allocated for a modern secretarial room, computer room and Media room . Other rooms were allocated for Transition Year Students.
In 1985 grants were given for a major extension to be built in two phases. The building was started on 6th September 1985 . The site for the development was donated by the Sisters.
June 2000 saw the last 20 boarders finish their education in Mount St. Michael and in August 2000 the remaining four sisters vacated the convent to live in a smaller house in the town and the C18th Georgian house went up for sale.