Speeding Ticket in a School Zone in Ohio

My son got a speeding ticket in a school zone in front of a vocational school. The signs posted on the side of the road do not have flashing lights. It simply has the fixed message School Speed limit 20. There is no assembly sign underneath that states what time or days of the week. The MUTCD states in Figure 7B-1 School Area Signs, there is a School Speed limit assembly which shows a sign underneath the speed limit sign with times or when children present or when flashing or mon-fri. On the MUTCD it is listed as Standard not guidance. Since the sign for this school does not have the proper assembly, would his ticket be invalid? I took pictures of the signs going in both directions to take to court. Please let me know if I have a case.

You most certainly do have evidence to present to the traffic court judge. Take the pictures and show him the statute when you go to court. It is worth a try since your insurance will go thru the roof if the ticket stands.

okay, do I plead No Contest or Not Guilty?

If you plead "no contest" and the court accepts the plea, the court will treat that as a guilty plea.

Okay, so we are going to court on Monday. I am to plead not guilty then they will summon the police officer that gave him the ticket and we will return at another date? At that time I show them my proof of information that the signs do not meet the standards.
Since we are in court twice, does that mean we have extra court costs if found guilty?

Traffic court matters are often handled all in one day - if you plead not guilty, there is usually a hearing that day. Verify procedures with the court. If you go to hearing and lose you can be assessed court costs in addition to the original fines.

So based on the facts and pictures that I have that show the signs have no attachment or flashing lights do you think I have a good chance of winning the not guilty plea?

The sign needs attachments or flashing lights, because.... ?

Otherwise the driver does not know when the 20 mph speed limit is in effect. Is it 24/7? Is there such a thing?

If you plead 'not guilty' in California, it's never handled the same day because a court date is set and the cop is summoned to appear. (You can, however, plead 'not guilty' to an infraction by mail and, thus, have only one court appearance.)
The price you pay for losing in court or pleading guilty is almost always exactly the same. You very well might even pay less by pleading your case in court and being found guilty, depending upon the circumstances. I'm sure that varies, widely, between different states.