Educational materials for kids are more than just books and videos these days. With Google returning 308,000,000 results for a search on “best apps for kids,” it’s safe to say mobile apps have made quite the entrance. But how do parents and teachers choose the best educational apps for kids?

As with other media types, apps are a tricky subject when it comes to quality control. While Hollywood has the MPAA guidelines to at least determine the age appropriateness of different films, apps are still too new to the scene to have that sort of overarching system.

However, there are some good resources out there. The Fred Rogers Center has put together a framework to rate apps for kids in terms of educational value and age appropriateness. The guidelines emphasize that apps should be “designed for active engagement” and “grounded in specific goals” that include “joint engagement” among kids, parents, teachers, caregivers, and siblings. The Center believes that apps should foster the well-being and development of children, with clear goals to educate, introduce new information, entertain, or develop specific skills.

The Center also suggests that apps should take into account the context in which the apps will be used. Are they meant for fun at home? In a classroom? With a group of friends or classmates? What development stage should the child be at to optimally enjoy the app?

The concept of developmental appropriateness is also a key element focused on by researchers at the Joan Ganz Cooney Center. The app should have a balance of features that can keep the child engaged, with rewards at various stages and the opportunity for adult involvement.

Ultimately, the most important part of choosing the best mobile apps for kids is to consider the specific kid in question. It’s also important to note that, as Colin Johnson, a teacher at the Stanford Laboratory School, says, no one evaluation schema is completely comprehensive. “It’s up to adults to think about their own values regarding children’s use of technology and find the tool that best aligns with those values,” Johnson said.

Whether it’s a star rating system, a list determined by a series of rigorous scientific testing, or one adult’s personal choice about what’s best for a child, choosing the best mobile app for a child is a complicated process unique to each user.