> Do US kids in science class use the metric system?

In general, yes. Though like everything else in the US education system, it’s really up to the local school boards. When I went through a couple of decades ago, we did almost everything in SI units with the occasional oddball problem in traditional units to make sure we knew how to do the conversions.

Your neighbours to the north do it the same way. In school (elementary, high school), all of the science classes are going to be in SI units, minus maybe a lesson or two in unit conversion. It wasn’t really until engineering school where they started really forcing us to be comfortable with problems that had a bunch of unit conversions; the engineers were really happy to give us problems with grams, pounds, miles, and litres, and expect us to get the right answers.

That sounds about right. I (vaguely) remember having to do some thermodynamics problems in BTUs and Rankine temperatures without converting to SI, but that was certainly the exception.

Once I got into the engineering curriculum, we were also expected to be able to do simple torque and force problems in pounds (force or mass, depending on context), feet (distance), foot-pounds (energy), and pound-feet (torque). Mostly it was to show that all the concepts work in both systems, I think. In case you found yourself working in an industry that hadn’t switched to metric.