Germany has a political scandal currently. A 40 year old politician had a sexual relationship with a 16 year old girl/woman. Jugendlicher, Teenager, Schulkind are afaik common terms in Germany with a juristic defintion. But are above terms clearly separated in daily usage/understanding, esp. in different regions (rural/urban/federal states)? Apart from relative age difference there seems to be a major debate mainly driven by different opinions/language when childhood ends (and therefore moral misbehaviour begins). Is Schulkind, containing the critical term Kind, at all widely used or more a rural term for very young school kids in elementary school?
Jugendlicher is a common, official and juristic term for young people not yet in the age of full criminal responsibility.
Teenager is adapted from the english term and refers to kids between the age of 13-19 ("teens").
Schulkinder are basically people going to school. Yes, it is basically more widely used for young kids going into their first few years in school.
Both Teenager and Jugendliche are fairly common in colloquial use. Jugendlicher seems to be getting a little less common and more old-fashioned, while Teenager is getting more common particularly among younger generations, but neither word would raise an eyebrow when referring to anyone between the ages of thirteen and twenty.
I've hardly ever heard anyone use the word "Schulkind" for a kid older than elementary school age, and never for anyone older than 7th grade or so.
From Wikipedia, about juristic definitions:
This Wikipedia article has a nice chart for the age groups.
There's of course the term Schulpflichtiger, which is someone that must go to school (i.e. did not yet finish the required nine years).
In everyday language, Teenager and Jugendlicher are used interchangeably (with Teenager not really limited to 10-19 (or rather 13-19, coming from the English term), typically starting later though). It depends on your age; older people may call anyone under thirty Jugendlicher ("diese Jugend!" / "die Jugend von heute!"). The term Kind is sometimes used for older Teenagers as well to emphasize an age difference. Schulkind roughly matches the juristic definition; Schüler might be a better (i.e. politically correct) word because it avoids the Kind and can be used for all ages. For elementary school, you may instead use Grundschüler.
Young people sometimes insist on being treated as adults; there is a blurry line between when you should call a girl a young woman, or a boy a young man, or say "Sie" to them. This may begin at about 16, and go up to the age of 20, and with this line, the terms to use move.
In the American usage, these terms would refer to different degrees of "minority" for the purposes of "age of consent" or "dating" eligibility.
"Kind" would refer to a child, someone up to the age of 12 of 13, (depending on the state), a "first degree" minor who is clearly not "dating" eligible.
Jugendlicher would refer to an older person, between 13-14 at the low end, and 16-17 at the upper end, or a "second degree" minor, who is more of an adolescent than a child, therefore "datable" by "nature," but not in the eyes of the law.
Teenager is a misleading term in this context. While it refers to ages 13-19, it spans all three categories; a 13-year old "Kind," a 14-17 year old "Jugendlicher," and an 18-19 year old of "full age" of consent.