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Since at least 1975 when a federal law was passed making metric the “preferred” measurement system.

In the 80s I was doing metric conversions in years 4 or 5.

I grew up in the U.S. We were taught to use the metric system throughout my schooling and used it (metric) for all science courses in university.

But in my university engineering labs on machining and machine tools, it was all taught in inches and feet. Not sure if that's because that's what industry used. I never entered my career as a manufacturing engineer.

For some odd reason, a lot of mechanical engineering and machining in the US is still done in inches and feet, though I think most of it is related to the defense sector. If you get into the automotive sector, for instance, you won't see that any more; they finally went all-metric in the 90s or so. Anything where the product is going to be sold internationally is probably metric.

In other engineering disciplines (except maybe civil), it's all metric. You won't hear EEs talking about semiconductor feature sizes in fractions of an inch.

Even back to the early 90's, it was the one and only unit system used in science classes.