cockerels and layers pellets

At the moment I am feeding my hens growers pellets with separate oyster shell and grit ad lib.  I started this when my two chicks joined the flock. 

I have one little hen and one not so little cockerel, both 12 weeks old.  Is it alright for the cockerel to eat layers pellets when he is a little older or should I stick to growers with separate oyster shell and grit for the whole flock?

I am not sure whether the raised calcium levels are OK for the cockerel.

Thanks Joy