To put it bluntly, absolutely not and I question where this history teacher got his information. It smacks of hearsay and old jingoism passed through multiple people. Or somehow the story of the Ross rifle has morphed into a knock against the French.

The Model of 1886 Lebel rifle was revolutionary when introduced as the first smokeless powder rifle. By World War I it was aging, and had some drawbacks as compared to the newer stripper clip loading rifles. In particular, its tubular magazine took longer to reload, it had a somewhat difficult to use sight--being very low to the barrel, which aided accuracy but was harder to use--and there were some issues with a lack of a top handguard causing soldiers to burn themselves.

However, the rifle itself and its 8mm Lebel cartridge were solid contenders in the trenches. The cartidge also ran the Chauchat automatic rifle, a workhorse of the western front in its own right and subject to its own staining of reputation by a conversion to the American .30-06 cartridge by factories pressed into service that could not really handle the job. Keep in mind that the main French arsenals were understandably quite busy in 1917 and 1918. The Lebel cartridge was quite similar in technology and design to 7.92 Mauser, .303 British, .30-06, 8mm Mannlicher, and even 7.62 Russian.

The 1886 Lebel itself also has good build quality from 1887 to end of military production in 1916. There is little evidence to suggest that they performed any worse in the trenches than the other mainline service rifles in the trenches. Wear and tear happens to everything after all. After the war, the French pushed projects to replace it though to a combination of factors some later build Lebels even remained in service into WWII and performed admirably in the battle of France despite their noticeable obsolescence by that point. In the end, over 3 million were built. Not the mark of a failure.

The other common rifle among French service was the Berthier, originally designed as a follow-on to the Lebel. This rifle did have some more issues in the trenches, particularly trouble with mud getting into its action and a low magazine capacity, the latter of which was resolved with a 1916 revision to change from a 3 round box magazine to a 5 round en-bloc clip. Like the Lebel, the Berthier was issued up to WWII, albeit in more specialized roles in its carbine form.

The Ross I mentioned earlier was a Canadian rifle that was designed in response to a lack of Lee-Enfield rifles from the British. While prized as a marksman's rifle it did suffer from a rather serious problem where the bolt could be incorrectly reassembled such that it could be closed without locking. Very good way to end up with a broken jaw. The Canadians quickly ditched them for Enfield rifles when possible, though snipers retained them for their accuracy as they could take better care of their guns not being in the first few trench lines.

And finally a word to French tactics--no, there are no instances where French soldiers were ordered to charge to conserve ammo except for perhaps small isolated commands at the very low level. The western front was an absolute meatgrinder, but the officers on the front by and large were not dumb--rather trying to deal with the realities of the emergence of what we now know as combined arms tactics. Remember that the vast majority of casualties in WWI were not inflicted by rifles or even machine guns but artillery.