It's great that you're considering all aspects of your son's education and well-being. Since he is social and loves learning, moving him to first grade mid-year could provide more challenging material and alleviate some boredom. This transition might enhance his engagement without significantly affecting his social life, especially if he adapts well to new environments. However, acceleration might require some adjustment time, so monitor his readiness and confidence. Discuss any concerns with teachers to ensure support. If keeping him with age peers, ensure the school can provide adequate enrichment. Ultimately, choose what seems best for his overall happiness and development.