A graduate of Glasgow University and Jordanhill education college, her first teaching appointment was to Garrowhill Primary in Baillieston.
Following the death of her mother, Miss Watt moved to Rothesay, on the Isle of Bute, where she was employed as a private tutor to the daughter of the Marquis of Bute. She was then appointed to teach mathematics at Rothesay Academy. A gifted teacher, she had the rare ability to convey to pupils the everyday situations in which mathematics could be of use.
She returned to Glasgow in the late 1950s after the death of her father, and became an assistant teacher of mathematics at Hillhead High before moving to the promoted post of principal teacher of mathematics at John Street Secondary in 1963.
It was a time of chronic teacher shortages - particularly for teachers of maths in the east end of Glasgow. This was a challenge to be met head on, and many a pupil in that school - and other schools too - was grateful to Miss Watt for going the extra mile with them.
In 1968, she shattered what was then the "glass ceiling" for female teachers, when she was promoted to the combined posts of depute head and principal of mathematics at John Street. This was also the era when the Alternative Syllabus in Mathematics was being introduced. Glasgow education committee had established a television service for its schools and Miss Watt was one of the presenters for the mathematics content.
With all this experience available to them, the committee appointed Miss Watt to the post of headteacher of Kingsridge Secondary in Drumchapel in 1974. The first appointment of a female headteacher to a secondary school in Scotland was big news and made a wonderful picture - the elegant and immaculately-groomed lady stepping out of her Triumph Spitfire sports car. The Times Educational Supplement Scotland profiled her on April 11, 1975, with the headline "The lady who made history".
After three years at Kingsridge, Miss Watt, in a sense, returned to where it had all begun, when she was appointed in 1977 as head of Bannerman High in Baillieston. Garrowhill Primary, her first school, was one of its feeder primaries.
In 1980 she acquired a toy poodle called Tuppence, which accompanied her to school every day. During the winter months they would arrive in matching coats, and on ceremonial occasions Tuppence would besport a coat in Bannerman colours.
Rena Watt served on the Independent Schools Tribunals in Scotland and the Munn Committee. In 1983, she retired from Bannerman High and from teaching.
It was only in the last four weeks of her life that she confided that she was in the latter stages of a terminal illness.