That's not true. Scholars have not long wondered about this question, because scholars have long presumed that Jesus and his fishermen apostles would have been illiterate — like most working-class people in Galilee.

Scholars have done meticulous (and quite boring for the non-specialist) work documenting low literacy levels in Galilee just to try to answer questions about Jesus's literacy and the literacy of his close associates.

Nobody has come up with any solid evidence that that would dispute Jesus's presumptive illiteracy. He was probably able to recite Hebrew passages from the Torah and the prophets, as religious ritual, much like many Jews do today. But Jews in Galilee in Jesus's time did not speak or read Hebrew with any real facility. Of the tiny percentage of Jews in Galilee who could read Hebrew, a far smaller percentage could write it. They didn't speak or read Greek either. Scholars are very sure about this for lots and lots of reasons. (Scholars who look at ancient literacy distinguish between the ability to read, which was very rare, and the ability to write, which was far more rare.)

To demonstrate that Jesus was an exception and to assert that he was literate in either Greek or Hebrew (beyond ritual purposes) would require very strong evidence. Experts in the field are practically unanimous in saying that if such evidence exists, it has not been discovered.