In 1969 the school got itself affiliated to CBSE and in March 1973, the first batch of Higher Secondary School (Class XI) appeared in the All India Secondary School Examination conducted by Central Board of Secondary Education, Delhi. When the new education system of 10+2 was introduced in 1976, the senior students of CST Shimla were redistributed to augment the strength of other CST's to make them viable as per newly introduced India's education system and CST Shimla remained Secondary School (Class X). On October 27, 1983, the main Torrential building which housed the girls' hostel and junior boys' hostel was gutted in a fire accident due to the electric short circuit. Fortunately, no loss of life occurred in the accident although it was a major fire during odd hours. Since then, a hostel building with an intake capacity of 350 children, a classroom block and a Library block have been constructed during the tenure of Shri. S.P. Datta, the then Secretary of CTSA. The school was upgraded to Senior Secondary (Class XII) level in the year 1987. Due to the generous funding Central Tibetan Schools Administration, Delhi under the Ministry of Human Resources & Development, Government of India, the school provides all the modern day facilities to students that include Smart Classroom, Computer Lab with Unlimited Broad Band Internet Access, Science laboratories, Library, Sports Facility, etc.
At present, the school is offering students in the senior classes the choice of studying Humanities and Food and Beverages.
