have a heart of gold

be as good as gold

be as hard as nails

be a nasty piece of work

Her heart's in the right place

be an awkward customer

be a pain in the neck

get on everyone's nerves

have your head screwed on

have a head for heights

have a head like a sieve

have a good head for figures

have your head in the clouds

be head and shoulders above someone

bury your head in the sand

keep your head

be an odd-ball

be over the top

go round the bend

be middle-of-the-road

be teacher's pet

be top of the class

be a big-head

be a lazy-bones

outside the classroom situation