Actually, I think it's correct as it is. "A number" is a singular thing (one number), no matter how many that number might actually be - therefore you can say:
"In most colleges there is
also a number
of staff who are particularly concerned..."
"In most colleges there are also staff who are particularly concerned..."
the latter implying more than one, i.e. some.
It is one of those semantics that is open to interpretation...
ANYWAY,, back to topic.......
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