My son hooked a new battery backwards in my riding mower, what damage did it do?
I am disabled and so I asked my teenage son to replace the battery on my riding mower. He got a new one, (the correct battery) and he hooked up the positive cable to the negative terminal and vice-versa. I had him switch them back and hook it up the right way, but now it only clicks loudly when you turn the key. What damage did he do?

if the battery is hooked up backwards it will click loudly but the bendix on the starter wont engage the flywheel.it may be backwards now! If you doublecheck it and it is hooked up correctly then it sounds like it just needs a charge.
Could have blown the battery and starter…..
damage the battery get a new or second hand one that work good
It is OK. You just need to charge it some, get a jump from a battery charger or your car, just enough to start it and let the thing run for a while to charge itself. ride around and have fun, you are OK!
Many new batteries (unless they are the 'sealed' type) come WITHOUT water in them now…. Which means you have to add the water, and then charge them, before you can use them. I'd be checking that first. (I guess they're cheaper to ship, and last longer on the shelf, without the water, lol).
Most mower batteries are 6 volt, not 12 volt, so be sure to set the charger to the correct setting.
Good Luck
The wrangler who posted before me is totally wrong sealed batteries cannot have water put in them and most are 12 volt 6 volt is very rare sounds like he fried the battery you can try charging it but good luck
I seriously doubt your son did any damage to your mower or it's battery. Like what was said, most small batteries like that don't come with a charge and sometimes don't even come with water in them. I would check that first and still make sure the battery is wired correctly.