Schooling may not be necessary for you to be a cop. As long as the minimum requirements are for HS degree only that is. If that is the case you have some things going for you.
At 30 you have considerable life experience and maturity over a 20-21 year old. As long as your work history is stable you should be fine. Departments are going to really appreciate your age. You are not on a level playing field with a 21 year old college graduate.
That being said if you are currently taking classes it indicates that you are serious about your future. You are making an investment in your career. Departments will like this.
I don't believe you will need the degree, just the ability to show you have started some classes and are looking to the future.
At your age you are going to have a harder time keeping up with the young pups who are in great physical shape. As soon as you think you are ready for the fitness portion of the applicant testing I'd say go for it.
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The beatings will continue until morale improves.