You might want to take a look at The Development of Technical Education in France 1500-1850 by Frederick Artz. It verifies that there was an artillery school at Strasbourg, but it should be noted that education in France, including technical education, was 'reformed' during the French Revolution beginning in 1789.

What are your references? I was under the impression that Hill was educated in England. He was commissioned in 1790 if I recall correctly. Would the British send a commissioned officer to a military school in France in the early 1790s?