Complex sentence: Joining immediately the School of Law and Modern History, and studying all summer, he took the examinations in that School in Autumn 1866 and received a second class this time, his examiners assessing that he had not mastered the details enough.
Split into simpler sentences: Joining immediately the School of Law and Modern History, and studying all summer, he took the examinations in that School in Autumn 1866. He received a second class this time, his examiners assessing that he had not mastered the details enough.