The establishment of La Salle School Klang was actually an idea from the Bishop of Malaya, Adrian Davales who saw the need for a school in Klang. The school was aimed to help students staying around Klang and far away places like Carey Island. In 1940, Adrian Devales requested Rev. Fr. Louis Guittat to start a school.

   So, with 37 students and one teacher, Fr. Guittat started St. Bernadette's School as a church private school in Our Lady of Lourdes Church compound on 15 January 1940. By 1941, there were three classes; two Primary One and one Primary Two. The following year, there were two teachers, Mrs. Dorothy de Zilva and Miss Stella Gabriel. The school fees paid then was $2.00. Fr. Guittat and his Building Committee collected donations door to door from the Catholic members of the church every month; dollar by dollar to build 4 classrooms. Even the ground floor of the building next to Letchuman Hall was also used as classrooms. Furniture and other equipment were collected from well wishers.

   On May 1947, Rev. Fr. John Edmund took charge of the school. By then, there were 210 students with six classes from Primary One to Standard Three. The number of teachers had increased to seven. The increase in the number of students forced Fr. Edmund to construct a wooden extension to the main building; and to rent a two storey private residence in Jalan Koto (Fort Road) to house the Standard Six and Standard Seven students. The school grew so fast that Fr. Edmund was unable to administer it with his heavy pastoral work. He requested the La Salle Brothers to take over the school. The Brothers agreed and the name of St. Bernadette's School was changed to La Salle Institution Klang. Then, the Bro. Visitor of La Salle Brothers purchased a lovely 12 acre piece of land along Telok Gadong Road on which the present La Salle Secondary School was built.

   On December 1951, Bro. Stephen Philip O'Callaghan was officially appointed as the first Bro. Director of La Salle Institution Klang. At that time, boys who intended to pursue the OSC examination after Standard Seven had to do a competitive examination to join the prestigious High School Klang and Anglo-Chinese School Klang. However, the standard of education of La Salle Klang was so high that these schools had stopped setting qualifiaction examination for Lasallians. Their excellent results int the OSC examination made their Alma Mater proud.

   During the head ship of Bro. Philip a few Brothers were appointed by the Bro. Visitor to help Bro. Philip administer the school. Bro. Provincial like Bro. Barnitus and Fintan accepted the responsibility for purchase of the school site and the planning of the original block of buildings. Bro. Aloysius and Martin collected funds to pay off the debts incurred. As the number of Brothers increased, they had to move out from the priest's parochial house to a rented house in Teluk Pulai Road.

   The present main block of 16 classrooms was built through fund raising functions organised by the Old Boys of St. John's Institution; and through lottery draws, funfairs and donations organised by the Brothers. By the end of 1956, the new La Salle School was ready. It was the first time that Lasallians saw new desks and cupboards in their new classrooms. On 21 February 1957, His Grace The Archbishop Emeritus Tan Sri Dominic Vendargon blessed and declared open the school.

   Bro. Leo Manicasani took over La Salle Institution Klang in 1958 while Bro. Philip went on to administer La Salle School PJ. With the foundation laid by Bro. Philip, Bro Leo added to the school two Science Laboratories, a school hall, the Lee Kuo Chuan Library, a building for the teaching of Woodwork, Metalwork, Electricity and Power Mechanics and also a three storey block containing four classrooms, an office and the teachers' room. In 1963, La Salle Institution Klang was split into La Salle Primary School and La Sale Secondary School. The La Salle Secondary School grew to a full secondary school with one Form 5 class.

   Bro. Celestine Jennings came in 1964 as the 3rd Bro. Director of La Salle Secondary School while Bro. Leo remained as the Bro. Director of La Salle Primary School. Bro. Celestine came from St. John's Institution and only directed La Salle Secondary Klang for one year.

   Bro. John Matthew Neo took over in 1965 as the 4th Bro. Director of the school. He was well known for his series of books known as "Fundamental Civics". The Secondary School grew rapidly and the school had to cope with an additional three Remove Classes and six Form Ones. In order to cope up with the expansion, temporary sheds were set up and even the library was converted into a classroom. Meanwhile, classes had to float and the old canteen was modified into a Science Laboratory.

   In 1968, Bro. Harold Reynolds came to La Salle Klang as the 5th Bro. Director. Before this, he was the Director of St. Joseph's Training College in Penang. During the derectorship of Bro. Harold, the school expanded to 27 classes. Extra-curricular activities were developed, namely the School Band, Boys' Scout, Red Crescent Society, Gymnastics and games. Students' Service Council (S.S.C.) was set up in 1969 to take care of the students' welfare. The new canteen was opened in 1971.

   In 1977, Bro. Cassian Pappu was appointed as the 6th Bro. Director ofLa Salle Secondary School. The school grew from an enrolment of 1080 students to 1380 students and from 27 classes to 38 classes. During Bro. Cassian's leadership, he successfully replaced the temporary shed by building a new 3 storey building with 12 classes, 3 Science labs and 1 A.V.A. Room at a cost of $270,000 which he raised through fund raising functions. Besides completing the school with new toilets and an extended canteen, he also restored the school field. The Parents' Teachers' Association and Old Lasallians Association of Klang were reactivated and they contributed tremendously towards the further development of the school. La Salle Secondary School became a prestigious school, excelling in both, academic and extra-curricular activities.

   Bro. David Liao came in 1983 to become the 7th Bro. Director. During Bro. David Liao's guidance, academic excellence was his top priority. He set up the computer centre in La Salle, making it the first school in Klang to have a computer centre. The results in the SRP and SPM examination improved, both in quantity and quality.

   The 8th Bro. Director, Bro. Michael Wong who took over in 1985 shared Bro. David Liao's vision and further developed the computer centre. Ten more units of computer were added through funds raised from a walkathon and donations. Besides that, Bro. Michael Wong saw to the repairs of the roads, school gate, roof top and plastered the 3 storey block.