It is not uncommon for a young male’s voice to change more than once! Voices rarely mature at an even rate. The larynx continues to develop beyond adolescence, and the voice can change significantly well into the 20’s, and then usually more slowly thereafter. During puberty, the falsetto* will be a bit wild and rough, and will not go very low. With time, the falsetto comes back and becomes possible below C4 (middle C) again, and uniting the registers in the new, more mature configuration becomes an important project. Later in adolescence or young adulthood, another noticeable change may occur.
This second change may or may not be accompanied by changes in the range of the chest voice, but the coordination with falsetto to form a full head voice is usually affected. The boys/men who have a second voice change may go from tenor to baritone, baritone to tenor, baritone to bass, or have a change in vocal weight or timbre.
Noticing as clearly as possible what the voice is doing presently, and making conditions better for improved functioning, will clear the way for where the voice needs to go. It’s best for the teacher and singer to withhold predictions about “where the voice is going”, and instead, work to make it freer and stronger, and allow a natural result.
*Call it “light mechanism”, “pure head”, “heady head”, etc. as you prefer.