Season 1: Freshman at Alfea
Season 2: Sophomore at Alfea
Season 3: Graduates from Alfea
Season 4: Professors at Alfea
Season 5: Freshman at Alfea again
Season 6: Sophomore at Alfea again

In Season 5, the Winx did go back to studying at Alfea. They live in the dorms, Ms. Faragonda and Professor Palladium were seen teaching the Winx about their powers and different kinds of magic, and last of all, the Winx were shown sitting and eating at the same table Alfea students were sitting and eating at.

yeah it is

Weird. :/

Yes, you graduated, move on with your life.

No one likes school that much.

Yes it is, but I thought they would continue to be professors, not students.

However it is weird but in the comics they technically never graduate and are still students furthering their training because Enchantix was the "ultimate fairy form" but once they gain new powers they still needed training with being the guardian fairy of their realms along with saving the Magic dimension.

They must really love school :P

not to me.

some people take extra years in college