I am going to try and find if there is any language research on this, but in the meantime, I'm interested in what your usage is. You can disguise your age by a decade or two if you like, but as you will see, it would have to be a whole decade.
I went to college 1971-1975. I say I went to college in the "early 70's." For K-12, especially K-8 (which we called "grammar school," not "elementary school" back then), I say "I went to school in the 60's" even though I started in 1958 and finished in 1971. For highschool,1967-71, I think I use the cumbersome "late 60's, early 70's" though I believe I avoid that altogether and just say "I graduated in 1971." What do you call the years you were at school? Don't fret if highschool and/or college don't fit into those neat four-year packets in your life, or they are complicated by putting immediate grad school onto the end of your undergrad, or technical school straight after highschool. That will just be part of understanding people's framing. I am looking for what people call early, mid, late, and what they summarise with a whole decade, as in "but then I went back to college in the '90's."
If it seems pertinent to the language question, feel free to expand your answer.