At this school, he developed a system he called "methodical signs", to teach his students how to read and write.

For example, where his system would elaborately construct the word "unintelligible" with a chain of five signs ("interior-understand-possible-adjective-not"), the deaf natural language would simply say "understand-impossible".

From this time French Sign Language flourished until the late 19th century when a schism developed between the manualist and oralist schools of thought.

This situation remained unchanged in France until the late 1970s, when the deaf community began to militate for greater recognition of sign language and for a bilingual education system.

In 1991 the National Assembly passed the Fabius law, officially authorising the use of LSF for the education of deaf children.