Why is “Out of School” NOT the idiomatic way to say “I'm learning material on my own, not as part of formal classes?”
Another person asked, "what can I say instead of “out of school” here?" which was canned as a duplicate of "Do you say “outside classes”, when mentioning study by yourself?"
No, and "out of school" has a completely different connotation!
I'm a native US English speaker. The phrase "out of school" generally has a specific meaning, used in telling someone something you are not supposed to be talking about, though there is a moral reason you should be. "I'm speaking out of school here." 'I shouldn't tell you why the....' (I'm telling you something that's confidential, or the management doesn't want known, though it should be, and I don't have authorization to speak.)
'Deep Throat' in "All the President's Men" was speaking out of school.
One would express the idea they were trying to convey like this: "Due to quarantine, I'm studying (a language, for example) 'on my own'."
"Self-study" implies a more formal course intended for self study, rather than picking up a book in another language and working your way through it.
One could also say, "I'm teaching myself to knit." "I'm working on learning German by myself" though 'on my own' would be more usual.
They wrote:
Do you say “outside classes”, when mentioning study by yourself? I
want to say that "now, I'm studying things other than what I learn in
school" with this present perfect sentence: Due to quarentine,(sp) I
have begun to study things out of school, especially languages.
Is out of school idiomatic in this context?
What could sound better?
which was actually a good question, just not the question they intended!
"Taking outside classes" would mean someone already in a formal course of study was supplementing it with “outside classes” from another source.