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Quoted from "eeltail"

I have a controller with an A and B schedule. A for the back yard and B for the front. I replaced three valves in the front yard with the water turned off (due to a broken valve) Once I turned the water back on to the front, one of the stations in the back yard came on. Can someone help?

Define "turned the water back on" - if you open a supply valve, and a zone is flowing water when it shouldn't, that's a mechanical problem in the zone valve. Unplug the controller, if you aren't certain. If you operate a controller to turn on the system, and an unwanted zone is on, that might still be a valve problem. Or a defective controller. Or bad wiring.

Quoted from "eeltail"

I have a controller with an A and B schedule. A for the back yard and B for the front. I replaced three valves in the front yard with the water turned off (due to a broken valve) Once I turned the water back on to the front, one of the stations in the back yard came on. Can someone help?

Sounds to me like you got some debris in the pipe when you replaced the valves in the front. Open the valve in question up and see if there is some debris in it. You may have damaged the diaphram of the valve that failed open as well due to the debris.