The United States has invested progressively more in education. According to the National Center for Education Statistics, in the 1961-62 school year, per-pupil spending was about $3,000 in constant 2014-15 dollars. In the 2012-13 school year, per-pupil spending was about $11,000 in 2014-15 dollars, more than three times as high.
Contributing to that trend is an increase over time in the ratio of teachers to students. The number of teachers in public schools has increased, from about 1.4 million in 1960 to more than 3 million today, and the number of students enrolled in public schools has increased from about 36 million to 50 million. This means that the average student-teacher ratio, reported by the National Center for Education Statistics, has dropped from about 26 students to every teacher, on average, in 1960 to about 16 students per teacher today.
While the average ratio has fallen, the change has not been uniform: according to a CPRE report on The Transformation of the Teaching Force, there has been a spike in pre-kindergarten teachers, for example, and a big increase in elementary enrichment and special education teachers.
Average teacher annual salaries have not changed substantially over time. According to the National Center for Education Statistics, the average U.S. teacher earned $52,830 in 1969-70 (in constant 2012-13 dollars), compared with $56,383 in 2012-13.