Tosefta su Esdra 3:76

A girl that has two [pubic] hairs is liable in every commandment stated in the Torah, [and may perform] either chalitzah or levirate marriage. And so too a boy that has two hairs is liable in every commandment stated in the Torah, and is fit to be a rebellious son or a teacher. Once his beard fills in, he is fit to lead the congregation in prayer, to pass in front of the Ark, and to lift his hands [for the priestly blessing], but he does not receive a portion of consecrated [foods] from the Temple until he grows two hairs. Rebbi says, I say, until he is 20 years old, as it is said (Ezra 3:8), "And they appointed the Levites from 20 years and upwards to oversee the work of the House of God."