Is it valid to recite Surat Al-Fatihah upon completing supplication at the end of academic lessons?

It is not legislated in Islamic law to conclude supplications by reciting Al-Fatiha or any other surahs, whether in lessons, sermons, or remembrance circles.

The Sunnah (definition) is to praise Allah and send blessings upon the Prophet (peace be upon him) at the end of a supplication. Imam Al-Nawawi stated that scholars have unanimously agreed upon the desirability of beginning and ending supplications in this manner.

The Prophet (peace be upon him) used to conclude his gatherings with the words: "Glory be to You, O Allah, and with Your praise, I bear witness that there is no god but You, I seek Your forgiveness and repent to You." It was narrated from Aisha (may Allah be pleased with her): "Whoever said good, it was sealed for him as a stamp upon that good; and whoever said evil, it would be an expiation for it."

Therefore, concluding supplications with Al-Fatiha is not from the Sunnah, and "whoever introduces into this matter of ours that which is not from it, it will be rejected," as the Messenger of Allah (peace be upon him) said. This hadith (definition) is a great principle for rejecting all innovations and newly invented matters.