Complex sentence: At the Collège he became a highly successful student, heading his class in all subjects except mathematics and the sciences, and many of his schoolmasters remarked upon the young student's ability to absorb great quantities of material.
Split into simpler sentences: At the Collège he became a highly successful student, heading his class in all subjects except mathematics and the sciences. Many of his schoolmasters remarked upon the young student's ability to absorb great quantities of material.