If it was my kid, and it is not, and he could commit to a better school then I project him to be able to get into without lacrosse and it is a large enough school to have a good variety of majors I can not see the down side - so what if he changes his mind and decommits he is in the same place he would have been anyway but without a fallback option. put a binder on the house but still look at other houses until contract is signed.
