26A School disturbed after losing Head, went downhill (8) I've got S???S?E? The first S comes from 17D Pardons one for initially usurping duties (7) for which I've got Excuses. Thanks in advance.
It's SCH ('school') plus a word for 'disturbed' losing its first character ('Head'), the definition being 'went downhill'. The word meaning 'disturbed' could legitimately be MUSSED (in the sense of 'disarranged') or FUSSED (in the sense of 'bothered') - take your pick!