Complex sentence: Today, his theory is supported and enriched by some of his students that have become University Lecturers or Professors in France and abroad, and still intellectually influences the English teachers, in French secondary and high schools, who attended Sorbonne Nouvelle University.
Split into simpler sentences: Today, his theory is supported and enriched by some of his students who have become University Lecturers or Professors in France and abroad. It still intellectually influences the teachers of English, in French secondary and grammar schools, who attended Sorbonne Nouvelle University.