Anytime I see this brought up, the consensus is that it’s not a good idea. Typically, kids don’t want to leave their friends and connections at one school after 3 years, missing out on the fun of senior year.
Added to that is that you need to make sure financial aid/merit doesn’t change when going from the first school to the second. Posters typically say that they believe kids don’t get the same level and have to pay more for the second.