Catholic schools, at least the one I go to, generally realise there are people of many faiths and beliefs and will let you draw your own conclusions and encourage you to ask questions about the faith.
Catholic schools are generally better are academic curriculum than public schools and challenge you to extend yourself and set higher goals for yourself.
Classes are generally relaxed as previously said and everyone loves one another. Of course if you are indeed, not Christian/Catholic there is always the possibility of a student/teacher (most likely student) trying to "convert" you. My suggestion to deal with this problem is to politely explain your beliefs and move on. Starting a huge thing over it is NOT a good idea seeing that 99.9 percent of all people will back him/her. However, them trying to convert you is unlikely. I mean, we're only 1 billion strong worldwide...
That being said, have fun!
