The student 'doesn't have it'
I have been talking with a delightful, mathematically resilient teacher who is exploring new pedagogic approaches to making maths ALIVE for her pupils: accessible, linked, inclusive, valued, engaging.
One of her students was described by a previous mathematics teacher as having "peaked; they just don't have it".
I suggest that, in the twenty-first century, with new knowledge of neuro-plasticity, this view represents not just a 'fixed mindset' ignorance of the excellent work of Carol Dweck, but also a practice of excluding certain kinds of learners; according to Bruner, amongst many others, all learners can progress but some may need an iconic or an enactive approach to concepts, to reduce the step-size and enable progression.
She and many other teachers have had success with algebra tiles; see for example: http://www.regentsprep.org/regents/math/algebra/teachres/ttiles.htm