I am never surprised when I read that good teachers impact their students beyond classroom academics.

However, the scope of a recently released study really impressed me. Researchers from Harvard and Columbia universities traced 2.5 million students over 20 years. The results? Good teachers make a lasting impression on their students, and their influence is felt for more years than previously believed. The study found that "students with top teachers are less likely to become pregnant as teenagers, more likely to enroll in college, and more likely to earn more money as adults."

The New York Times article "Big Study Links Good Teachers to Lasting Gain" reports that while the teachers' value-added scores might vary from year to year, good teachers consistently rose to the top. I'm aware that the subject "value-added" is controversial, yet this study's depth and breadth should make all educators take note.

Some of the findings include:

• A student with one excellent teacher for one year between fourth and eighth grade would gain $4,600 in lifetime income, compared to a student of similar demographics who has an average teacher.
 
• The student with the excellent teacher would also be 0.5 percent more likely to attend college.
• Replacing a poor teacher with an average one would raise a single classroom's lifetime earnings by an estimated $266,000.