Sweets seem doubly good when starting school (7)

'sweets' is the definition.
(bonbon is a kind of sweet)

'doubly good when starting school' is the wordplay.
'doubly' shows that letters should be duplicated.
'good' becomes 'bon' (I've seen this in other clues).
'when starting' suggests taking the first letters.
The initial letter of 'school' is 's'.
'bon' doubled is 'bonbon'.
'bonbon'+'s'='BONBONS'

'seem' acts as a link.
This may not be right. It may be part of another bit of the clue.

Can you help me to learn more?