The Assumption Sisters, together with Sister Ma. Nathaniel Rocero, SPC, left Santiago in April 1978 to answer the call of other areas where they were most needed. The same year marked the appointment of two lay persons, both alumnae of La Salette of Santiago, in the highest academic position of the school. Mrs. Gloria C. Yco took over the Academic Dean of the College Department while Ms. Iluminada Silverio was appointed Principal of the high school department.

Both department and their faculty grew and developed with the zeal and commitment manifested by their lay managers who worked with them from 1978 to 1979, the Daughters of Charity came over to assist the La Salette Missionaries in the supervision of the college department while Mrs. Silverio continued her leadership in the high school. Under her leadership, the science curriculum was approved and school year 1981-82 saw the first graduates of the Science Curriculum.

The succeeding years saw La Salette High School in its commitment to quality education as the administration, faculty and staff worked diligently and painstakingly towards accreditation. In school year 1983-84, the High School underwent its first formal PAASCU preliminary institutional survey and since then, efforts were geared towards achieving the greatest mark of academic excellence – the PAASCU accreditation. While the school achieved greater heights, however, the PASSCU requirements necessitated full time principal for La Salette of Santiago to cope with its growing needs. Mrs. Iluminada Silverio, then the Vice Mayor of Isabela, transferred to the college department where his field of specialization was needed and Mrs. Clarita Javier took over in 1985 as full time principal of La Salette of Santiago, High School Department. On April 17, 1985, the La Salette of Santiago, High School Department achieved its level I – Accreditation from the Philippine Accrediting Association of Schools, Colleges and Universities (PAASCU) and Foundation of Accrediting Agencies in the Philippines (FAAP).

Some pessimistic and superstitious believe that for every good fortune, there is a corresponding misfortune. As if confirm this, on March 25, 1986, La Salette suffered its second setback when the fire of unknown  origin razed the main building to the grounds and  left an unprecedented damage consisting the school of millions of pesos in terms of damaged properties and buildings. The summer 1986 saw the frantic efforts of the Administration, Faculty and Staff in raising funds and soliciting financial and other assistance from here and abroad.

School Years 1986 through 1988 were fraught with major problems arising from lack of classrooms, retrenched teachers, overloads, lawsuits and the concomitant financial difficulties. Only through the concerted efforts of the Administration headed by Fr. Constante Dannug, MS as the Rector and Sr. Saturnina Pascual, SNDS as the Principal, the faculty, staff, students, the Home and School Association (HSA), the Community and School Board (core group includes the late Cong. Antonio Abaya, Engr. Ramos, Antonio B. Santos, the late El Ben Co)  and with and by the grace of God a new building was constructed and the school was able to stand on firmer ground.