Yes. FlipaClip is the best mobile-to-desktop animation bridge on the market. While getting it "unblocked" requires either Google Play Games, a smart proxy, or a fallback like Piskel, the creative payoff is massive.
Final recommendation: Use the official Google Play Games Beta on your home PC to master the tool, then use Piskel at school. Never trust a "free APK" site. Animation is a skill that pays off—don't let a firewall stop your storyboard.
Many people misspell FlipaClip as "FlipClip." Consequently, several mirror sites exist. flipclip.net (unofficial) offers a similar raster animation tool. While not the real app, it saves as MP4 and bypasses "FlipaClip" keyword blocks.
Don't redraw your background in every single frame!