"Do you know a good school?"
Translation:Te ismersz egy jó iskolát?
I believe it's similar to German kennen/wissen, French connaître/savoir, Italian cognoscere/sapere, Spanish conocer/saber -- ismer is "be acquainted with" (a person or place) while tud is "know" (a fact). (And tud is also used for "know how to (do something), be able to (do something)".)
If you put it at the end it means the "school" is the focus. So you know lots of things - an PM, a great doctor ...but do you know a good SCHOOL?
Because a good school is indefinite, so we use the indefinite conjugation.
If you had known the good school or that good school or something like that, it would have been definite.