Recently we found significant crosscultural gaps in some scales like SDQ or PEDSQoL and submited papers. This raised a question for me: what are your thoghts about "best" general measurement scale?
I have used CBCL in research setting in a variety of set ups. It has a range of intruments that over the full age span. It gives cosolidated score for each dimensions. It does not require children to be 'boxed' into categories as its difficult to always come to firm diagnosis without several informants/observations (e.g. in school). CBCL group of instruments can be used on the basis of parent rating or teacher rating or even self rating for some instruments. There are cutoffs for various societies across the world.
I agree with Soumitra that the CBCL and its complemantary scale for the child/adolescent, which is the Youth Self Report, are good. I'd also recommend the Voice DISC which checks for DSM diagnoses. I'm not sure if it has been updated for the DSM-5 though.
The only problem with these measures is they don't cater for Social Desirability in young people. The RCMAS-2 caters for this and is also an ok overall scale.
Regardless of the measure you use, I'd strongly recommend including something that assesses for the issue of Social Desirabiltiy. This is too why researchers have recommended informant reports from a variety of sources e.g. teacher, parent, peer, coach etc, as young people have been shown to act differently depending on the social situation they are in.
Accuratley assessing young people is a tricky area both because of social desirability and also because many have a lack of emotional self-awareness e.g. they aren't aware of their own symptoms of anxiety actually being anxiety.