Balancing academic, social, and spiritual needs can become quite a juggling act. It seems that you have thought through this situation already and your son has expressed a strong desire for being around his peers.
Each child is different and has different needs. The Catholic middle school may very well meet the social needs of your son. If you work through this process with him, both of you can make sure that his spiritual needs are met as well. That may mean a home school class on the faith every Sunday or extra work during the summer.
Before beginning middle school, you may wish to state your expectations clearly. Middle schoolers have a tendency to join, join, join and become over-involved in sports and clubs to the point that their grades suffer. A slight decline in grades is to be expected, but not dropping an entire letter grade. Because of their involvement in various activities, many middle schoolers may not be getting enough sleep. So you may wish to set reasonable limits.
Team sports and clubs are wonderful for children at this age. They need to learn and practice social skills, and if your home schooling situation does not provide some of these opportunities, some children may feel deprived. Some children need more social interaction than others, and this is the way God made them.
God bless you and your family as you work together to make the right decision.