@Ariella – re: black jackets and hats
Your son will soon conform to the conditions that his friends keep. My sons went to a modern yeshiva but one of their classmates wore black hat and black jacket… and he was well-liked and held in high esteem by the other bochrim.
Don’t choose the yeshiva by the dress code is a good idea. Choose it by the middos you see the bochrim embodying and the menahelim embracing. Watched the news lately? There are too many yidden hiding under their black uniforms who have hearts of black and many good yidden wearing all manner of dress who have hearts of gold. Go for the gold.