I find that at least 1 in 3 club aircraft have compasses that show say for example 360 on 360, 085 on 090, 185 on 180 and 260 on 270.
So that every time the student turns onto a new hdg. the compass needs re-setting.
I always have my students cross check the compass/DI with runway hdg. this is when the errors usually show up.
(Yes the runway mag. hdg is taken into account, pitot on/off, radios on/off as req. and who knows whats buried under the runway).