Me and my mom found this riding stable and I’m taking lessons in the summer but how do I know its good? All the horses look healthy and happy. The stable looks really old and like dirty kind of thing. They have boarders and they seem happy with it. I’m 13 and 105 pounds are they gonna put me on a pony? I’m 5’10 too so. I went horse back riding for girl scouts but they held the horses and we rode in a circle and they taught us how to turn the horse, stop it, make it walk and trot.
Are all the horses well fed, adequate turnout, blankets as needed? Do all the horses have shelter and water available 24-7? Do all the horses appear to be up to date on their farrier work?
If the answer is yes then the horses are well cared for.
If you see horses that are turned out in cold weather in the pouring rain with no blanket and nothing but a tree to stand under knee deep in mud and poop, empty water buckets, underweight horses that are lame or in need of a hoof trim, that is a bad place.
Define dirty? No barn is every truly clean because there is dust in the shavings, dust in the hay, dander on the horses’ coats. Are the water buckets clean with clean water in them? Are the stalls respectably clean? That’s a good place.
If you see dirty murky water in horse stalls (hay is fine, maybe a little grain but you should ALWAYS be able to see to the bottom of the bucket), walk by a stall so dirty that your eyes burn and there’s junk cluttering the aisles, that’s a bad place.
At 5’10 no decent trainer is going to put you on a pony. When you are as slim as you are the concern will be to find a match based on your height, not your weight.
Do you know whether your horse is the right weight? Believe it or not, more than 80 per cent of all leisure horses in the UK — from Thoroughbreds to cob types — are overweight. 
Clinton shows you how to teach your horse to lead properly.
Leah and Gigi at Germantown under Shannyn Welsh instruction.