The rabbeim and teachers (for Sem) in American are amazing. In EY it is often on a different level alltogether.
That said, be carefull that you send to the right program, no matter where they are. I have seen some seminaries (not saying where) that were run as money factories with little attention paid to the young women beyond enforcing strict rules. As a parent, this is so disappointing, considering what amazing options there are out there.
That said, the ability to live on another plain for a year or two, to live in a culture that values torah in a different way is special. The ability to daven and experience yahadus on a different level, to experience a shabbos in Tsfat with a family that has nothing, but invites the whole world over anyway, to experience Bnei Brak, to experience a shabbos with the amazing communities of Olim in (Ramat and) Bet Shemesh, to experience a shabbos in a yishuv where people are moser nefesh for yishuv ha’aretz, these are not things you get in NY of NJ. There is nothing wrong with the US or the UK. But EY is ours. It’s where we belong. And sending your teens here for a year or three sends a message about what matters most. Before we go to college, before we get married, we orient ourselves towards who we really should strive to be, and what kind of lives we want to live. We give our young men and women a choice, we send them off, we show them our trust and let them discover themselves in a fairly safe and growth driven environment. What a beautiful commitment to our children.