Originally Posted by LapLap

The “filtro de seguridad” for families at BCN is for families travelling with young children (specifically - niños de corta edad).

A child in Spain is generally thought of as a young person who hasn’t yet reached adolescence. But in this case, it’s really for families where at least one member isn’t autonomous enough to deal with their own luggage and who can’t be counted on to respond to requests and instructions from Airport workers.
If the youngest child in the family is an adolescent but has a disability of some kind, there would be no solid guidelines as to whether they should use this “filtro” or the one specifically for those with disabilities.

Whether a family with a very able looking 13 year old or 15 year would be stopped or not may well be down to whoever was manning the “filtro” at the time. If the youngest kid is clearly pre-adolescent there should be no problem. But “corta edad” literally means “short age” up to 9. 10 and over are “longer” numbers. So 9 is the “I’ve got every right to use this lane” cut off point if that’s what you’re after.