I didn't have a traditional 'high-school' class thing. So your comparison is invalid.
There is almost no Hebrew language in any of my daily life. But I do still read it.
You are barking up the wrong tree, because not everyone is like you, and had the life you have had.
Your conclusions are parochial, and apply only to you.
/johnny
Try decades later. Try when they’re no longer in school so the data just isn’t useful to them anymore. Again, try yourself. How much do you really truly remember pow right off the top of your head, even if you didn’t do the traditional school thing you clearly know stuff, but how much retrieval was there.
Hebrew’s not in your daily life. But is it in your weekly life? Monthly? Clearly it’s in there sometimes if you still read it. I spent 7 years in various point of school learning German. At this point multiple decades later the only German I know is stuff from Frank Zappa lyrics, yeah maybe there’s a hundred words that ring a bell and I can suss some stuff out but I can’t read German anymore. I wish I could, but my life didn’t go in a direction to use all that German I learned, so it’s gone... well not GONE, it’s down there somewhere and 1 or 2 classes could probably dredge it back up. But even if I did that, if I didn’t use it after it would sink to the bottom again.
No my conclusions are based on well grounded psychology and teaching research. This is how human brains work, data you put into them that you don’t retrieve periodically sink to harder to retrieve places. Even folks that use various memory tricks like mind castles still find rooms that get “dusty” and take more work to get back.