You both have parental responisbility for your son and he has a right to a close relationship with both of you
However you are no longer one family unit which means that the arrangements will of necessity change.
Every child and every family is different so there is no one size fits all answer to ocntact arrangements.
Generally the ocurt likes to ensure that both parents have weekends with their child - so alternate weekends are the most usual - if you can adjust your working hours then from school on a Froday to school on a Monday will work - but only if you willnot need Breakfast club (unless your ex will also need it in which case that is fine)
One or two evenings in a week is also usual - or a night if you can avoid the breakfast club issue.
Assuming you can have the time off then half of the school holidays is also reasonable.
There is a lot of information about Parenting Plans on the CAFCASS website.
If you cannot reach agreement - using Family mediation if necessary then you can apply to the court for an ordersetting out the time he spends with each of you
I hope that this is of assistance - please ask if you need further details