Is there a way to prepare for common entrance when the child is in the state school - year 7/8?

thank you

I think the usual answer is "with difficulty" . Presume this is for Harrow or somewhere like that?

The exam is different from the National Curriculum and children who who take it tend go to preparatory schools which are named that for a reason - they prepare the children.

I think if you have a very bright child who can cope with GS work while studying for CE and you also have a good tutor familiar with CE it may be OK but it would depend on which Public School you are targeting as some are much much harder than others