The "Prajna Paramita Hrdaya Sutra" is also called as "Heart Sutra". This Sutra can be said as the most common Sutra recited by Buddhist followers of the world. It's also a very short Sutra for those who practise "Avalokiteshvara Dharma Door". This Sutra is also said to be a Sutra for increasing wisdom. And thus it's very popular and easier to remember compared to other Sutras. And that's why for those early learners like children, they tend to start memorizing this Sutra.
This "Heart Sutra" has many different version (of course with the same meaning). It has Pali, Sanskrit, Chinese and perhaps version in other languages. But, I think the Chinese version is the most common one. You can also find "children version" of Heart Sutra. And the video below is the children voice Heart Sutra.