I find the ones people are really worried about present themselves (or the teachers do) around school, asking for support etc, but I also try and do cover once a term in each class so I spot any lost souls who are slipping under the radar.
I do observations following pupil progress when teachers flag children up as struggling and also a lot of those children are the same ones whose parents pop into see me or see Pastoral & get referred to me to do Early Help Assessments. EHA gives me a very good feel for whether it’s global, specific, asd, adhd, attachment etc as I’ve had all the back story.
In addition I teach a group intervention 9.30-12 mon-thurs for up to 8 learners on PIVATS.