Multiplication aids one son's forgotten in arrangements for school classes (10)

'multiplication aids one son's forgotten' is the definition.
I can't judge whether this defines the answer.

'arrangements for school classes' is the wordplay.
'arrangements' becomes 'tables' (table is a kind of arrangement).
'for' says to put letters next to each other (I've seen this in other clues).
'school classes' becomes 'time' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'tables' put after 'time' is 'TIMETABLES'.

'in' acts as a link.

Can you help me to learn more?