A lot of dentists may even prefer uncertified assistants if there aren't any good programs in the area; they say they'd rather train them in their own ways than have them waste a year and learn lots of mistakes. Totally depends on the school and the state.
However, in MOST states it is illegal to take x-rays and do certain procedures (like polishing) without being certified. In that case, if you don't want to do the year course, many schools can just offer the xray cert with a weekend course.
I'd recommend it! Great experience. If not that, then perhaps starting to train as a lab tech...