What you learned in school
Medical textbooks described tonsils as vestigial organs with no important function - evolutionary leftovers that served no purpose in modern humans. Students learned that tonsils were "portals of infection" that should be removed preventively to avoid future illness. Tonsillectomy was routine surgery performed on millions of children annually, often combined with adenoid removal. The procedure peaked in the 1950s when it was considered standard preventive care.
What we know now
For much of the 20th century, tonsils were considered vestigial organs with no important function. Many children had their tonsils removed preventively to avoid future infections. It was routine surgery, often done along with adenoid removal. Medical schools taught that tonsils were evolutionary leftovers. We now know that tonsils are important parts of the immune system, particularly in childhood. They help develop immune responses and contain infection-fighting cells. Preventive removal is no longer recommended except in specific medical circumstances.