I have standardbreds some at the track and some in the backyard. I am wondering what you mean by racing. Was your horse a trotter or a pacer? If you mean when he acts like he is racing that he starts to pace there are things you can do for that. Some former pacers (when both legs on the same side move at the same time) will pace when they are worried or excited. What kind of work/riding are you looking to do with your horse?
There are a number of resources such as this one: All About Standardbreds: Teaching your Standardbred to Trot (and not pace)
I agree to an extent about restarting them from the ground. You have to remember that in general, most standardbreds have more ground manners and training than most thoroughbreds. If a Standardbred is going to race in the 7th race it will be harnessed and warm up before the 5th race. It will then spend the time between the two races standing in harness. I would focus more on bending and lateral work. What bit do you have your standardbred in? I have heard from a few people who find that their standardbreds ride better in a three piece bit (like a french link). They are raced in a snaffle so that can put them in a different mind set.
How old is your horse? Where was your horse before you got them ie off the track or from a field? The age and how long your horse spends at the track will impact how long it takes for them to understand that they don't need to race. They tend to be very willing horses once they have a little trust in you.