I'd say it is almost OK. You would not normally 'catch' a seat, but you can catch a bus. So, maybe you can say "I leave my house early in the morning to get a seat in the bus on my way to school."

you can simplify it to: "catch the bus". 'I leave my house early in the moring to catch the bus on my way to school.' :)

It's perfectly OK. "Catching the bus" is a normal way to say you're going to get on a bus. Also, in your sentence, you're implying that if you leave your house too late, you'll miss the bus. (btw for the above post, I think you should keep the "bus" part in the sentence b/c "seat" could also be referring to a seat on a train or car)

I leave the house early in the morning SO I CAN GET A SEAT on my way to school. OR ... so I can FIND a seat ... the idea here is that later buses are more crowded so this way you can sit during the bus ride.

well for me its ok.. its a slang word.. like for example' hit me on the phone means call me.