English Explanation of Pirkei Avot 5:21

He used to say:
At five years of age the study of Scripture;
At ten the study of Mishnah;
At thirteen subject to the commandments;
At fifteen the study of Talmud;
At eighteen the bridal canopy;
At twenty for pursuit [of livelihood];
At thirty the peak of strength;
At forty wisdom;
At fifty able to give counsel;
At sixty old age;
At seventy fullness of years;
At eighty the age of “strength”;
At ninety a bent body;
At one hundred, as good as dead and gone completely out of the world.
This mishnah gives ages that are appropriate for the different stages in life. We should note that in most places in the Mishnah, the age at which a child is obligated or allowed to do something is dependent not on his true age but either on his/her physical or mental development. Indeed this mishnah, which lists true ages, is probably more of a guide and not to meant to be legally binding. The Meiri states that it is meant as a stimulus to parents to teach their children the right subject at the right time. In modern times we also give rough ages of development but realize that some children will be quicker to reach those milestones and some will be slower.
Although this mishnah begins “he used to say” and therefore seems to be Judah ben Tema’s words, according to the Tosafot Yom Tov it is actually the words of Shmuel Hakatan. As we noted in the previous mishnah, this mishnah and the next two are addenda to tractate Avoth.
At five years of age the study of Scripture: Some interpret this to mean that at five the child should begin formal schooling, where he will first learn how to read the words of Scripture and later understand them. Interestingly, in modern times it is still typical to begin to learn to read at five.
At ten the study of Mishnah: The study of mishnah refers not to the study of the Mishnah as we have it today, but rather to the rote memorization of brief, usually halakhic material, which is the literary format of most of the Mishnah.
At thirteen subject to the commandments: At thirteen a child is liable for his own sins. This was the average age of puberty at the time of the Mishnah. This is the earliest reference to “bar-mitzvah” in Talmudic literature. The concept of a celebration of the bar-mitzvah does not appear until the fifteenth century. The idea of a “bat-mitzvah” does not appear until the 19th century.
At fifteen the study of Talmud: Talmud refers to the learning of the reasons and the Biblical proof of the laws that are “mishnah”. At this age the child is more intellectually developed and can begin to learn the more difficult material. Note that most children probably did not go to school this long. The mishnah is referring to an ideal and not to common practice.
At eighteen the bridal canopy: According to many scholars, this is also an ideal. In practice men (but not necessarily women) got married later.
At twenty for pursuit [of livelihood]: Once he has married a woman and had a child or two, he must pursue means to support his family. By twenty a person should have a profession. Others interpret this to mean that at twenty a person stops learning Torah and begins to work. Still others interpret this to mean that at twenty he pursues the enemy in war. This is the age at which one is liable to join the army, according to the Torah (Numbers 1:3).
At thirty the peak of strength: At thirty a person is at the peak of his strength. In the Torah the Levites only begin to work in the Tabernacle at thirty (see Numbers 4:47).
At forty wisdom: At forty a person’s wisdom comes to fruition. This is traditionally the age at which a person can be considered a “rabbi”. Nowadays people becomes rabbis at a much earlier age.
At fifty able to give counsel: In order to give advice a person needs to be wise but he also needs experience. At fifty a person still has the wisdom he reached at forty, and he now has the experience needed to advise others.
At sixty old age: A person enters old age at 60. Interestingly, the retiring age in our society is usually considered 65 (although in our society, with its advances in nutrition and health care, people are often able to work well past this age).
At seventy fullness of years: David died at 70 years of age, and I Chronicles 29:28 states, “And David died at a full age”.
At eighty the age of “strength”: See Psalms 90:10, which states that the given strength, one can live until 80.
At ninety a bent body: We should note that in the time of the Mishnah it was probably quite unusual to live this long.
At one hundred, as good as dead and gone completely out of the world: In the time of the Mishnah one who lived to one hundred probably could not see or walk, and was probably extremely senile. This mishnah considers such a person as good as dead. If you are over one hundred and you are reading this or even having someone read it to you, a hearty Mazal Tov. You have outlived the mishnah’s wildest dreams. And for the rest of you, may you live and continue to learn until 120!