That really depends on the high school in question, in NL the mandatory curriculum is laughably bad, mostly due to a lack of competent CS teachers. We teach Jav

That really depends on the high school in question, in NL the mandatory curriculum is laughably bad, mostly due to a lack of competent CS teachers. We teach JavaScript, basics of HTML and CSS, React & React Native, PHP (although I’m trying to get them to replace that with JS) , algorithmic complexity (to the level of handwavy big-O notation and some sorting algorithms), basics of UML, PostgreSQL, C in the context of Arduino, state machines, and for the advanced students I try to throw in a bit of TLA+ (mixed success there). We try and use a project based system where the students pick a project with an actual company and implement a proof of concept level solution. Last year that was a warehousing robot, this year a smart home solution to lower energy costs in social housing. Other non company related projects are a rubiks cube solving bot using LEGO Mindstorms along with a TLA+ proof it could actually achieve every position and would terminate (I did help out a bit on the TLA+ stuff ofcourse). The trick is to never tell students how advanced the stuff they're doing is, get them excited and they'll go further than you can imagine. But then again, I am also lucky enough to teach at a combined middle/high school that basically took the last 3 years of the curriculum (15-18yo) and shoved them into the first three (12-15yo) so I basically get free reign since they covered the final exam stuff in the first three years already. I don’t know of any other high school in the country that has this model and teaches at this level. In fact, that is the only reason I teach part-time at all: I wouldn't want to be an actual teacher, but they needed somebody with a deep enough technical knowledge, and had me in the picture both as an ex student (from before they introduced this CS-stuff though, I still deeply envy my own students) and as a 'client' of the students from my previous employer. Eventually I agreed to teach one day a week. Generally you can expect basics of HTML, CSS, PHP, and if you’re lucky a bit of Arduino-C out of high schoolers, if they get CS at all (it’s very much optional for schools to provide a CS track in NL)