Sorry didnt see that yourr topping most subjects, id recommend u stay then. Only a top 10 school would benefit u and thats provided u maintain ut good performances in a new environment
if the selective school is in the top 30 then you'd be better off moving, 300+ is quite bad tbh and you seem like you'll settle very easily in a new environment since you get along well in your school. However if you're performing well in your school, like top 5 all subjects then maybe staying...