I see this question a lot! You were smart to reveal that you live in Ohio, because this law can vary from state to state and in different countries.
It's funny and amusing how the answers are all over the board on this one. It just goes to show you that very few actually know what the law says. First let me compliment you on erring on the side of caution and stopping for a bus on the opposite side of a four lane road. I had faced the same dilemma before myself and I also wondered if I had to stop. (And I also live in Ohio) One time, not long after I did stop in this situation, the driver of the bus actually waved me on. So I checked into it with some law enforcement friends of mine...
It may surprise many, but "lookin_...", "moncalvini", and "Mr.Knowitall" have it absolutely correct. You do not have to stop on a four lane road if you are traveling in the opposite direction. The road does not have to have a center lane or be a divided highway. If it's 4 lanes or more with 2-way traffic. You are okay to proceed with caution. (This is because it is also ILLEGAL for the children to cross in front on the bus when the road has 4 or more lanes.) The BMV site is a bit confusing because it implies more than one roadway, but the actual ORC defines it rather well. See section 4511.75, paragraphs (c), and (d). C-Permits traffic in oposite direction to proceed and D-Limits the taking on and discharge of passengers to the side of the road the bus stops on.
Between you, me, and the rest of the 1 million + people who participate on this site, I'd still slow way down for this situation.
Thanks again for asking and being specific about where you lived so we could give you good answers.
Be safe. God Bless.