Do frogs lay eggs twice a year?

Our pool wasn’t uncovered this year and became a backyard pond. It was filled with at least 1,000 tadpoles who developed into frogs in early July. By the end of July, there is another batch of hundreds of tadpoles growing their first legs. And, just two days ago, after a great deal of croaking, we watched a female leap into the “pond” (where the tadpoles from the second “litter” are still developing) and several males leap in after her. Is this normal behavior or is it unusual?