There are four things wrong with the way foreign language is taught in US high schools.
First, it is taught late. Language learning potential declines dramatically after age 12.
Second, classroom language instruction based on simple memorization is artificial and inefficient. Total immersion works much better.
Third, in the US, there is rarely any follow-up. The learning atrophies because there are few opportunities to use it.
Fourth, it is taught backwards. Natural language learning involves vocabulary learned by listening followed by reading followed by academic exposure to grammar.