This question is inspired by several similar questions on this site.

The scenario: at one moment, all people above the age X disappear without a trace. How low this X can be that human civilization survives?

Obviously, 1 year old is too young, and 18 is arguably too old.

I set the following criteria of success:

• Language is kept (which may change with time, it's Ok);
• Tech level above stone age is maintained (at least in some communities). Scavenging is Ok for as long as people are able to scavenge; no mining or smelting is needed up until that point;
• Sufficient artifacts and knowledge from our current civilization survives, so, eventually, younger civilization can utilize it for a "reboot".

Children don't have to maintain world in order after the event. Any level of chaos, regression and massive dying is acceptable if the rules above are satisfied.

P.S. Extra bit of information - there are apparently more than a few children under the age of 18 (likely thousands, if not tens of thousands) who are familiar with Survivalism. A proper "failure" scenario should mention how all of those children will be eliminated, or isolated for the rest of their lives.