I think it really depends on what you feel your school offers and what you feel your child needs.
My older son had been in a Montessori. There was no formal art class, so we did saturday art classes at the local art center. There was no music class, so we started piano lessons. No gym class, so we started the swim team. No real science, so I bought an online thing where every month, we did little science experiments. No spelling, so I made spelling words each week.
After awhile, I realized, why are we paying tuition for this and moved to the (free) public school! We still do some of these activities b/c they are fun, but we started all of them to fill gaps in his education that we thought he needed.
