Transferring to another school as a senior is usually not recommended. There are a few reasons why. First, as you mentioned, there are not so many schools that allow this type of transfer. Honestly, schools would possibly see that you would want to receive a high school diploma after just a year of stay and that does not sound good to them. Schools care more about students' growth as they become valuable part of their communities throughout entire school years. Secondly from college counseling point of view, this transfer does not any give positive view on you either, unless you present exceptional reasons why you transferred to a particular school at the senior year, and still this makes college admission office wonder why you did. Also, most elements of college application preparation will be done by your junior year; your transcript in junior year will be more important than that in senior year and your activities until junior year will be considered more as colleges review your file.。