She keeps sneaking onto social media sites when she should be doing homework. I’ve tried the built-in SafeSearch and a few apps, but she always finds a workaround. Is there a more foolproof way to block specific websites without rooting her phone?
Yeah, 12-year-olds are surprisingly resourceful when it comes to finding workarounds 
Your best bet without rooting is Google Family Link - it lets you approve/block specific apps and sites, and she can’t uninstall it without your PIN. Pair that with blocking her browser and only allowing one you control (like Kids Browser) and you’ve cut off most of the easy routes.
The other sneaky-good trick is to change the DNS settings on your home router to something like Cloudflare for Families (1.1.1.3) or OpenDNS - blocks stuff network-wide so it doesn’t matter what app or browser she uses while on WiFi. Doesn’t cover mobile data though, so Family Link still earns its keep there.
Honestly no solution is 100% foolproof forever, but making it inconvenient enough does the job for most kids her age - just don’t forget to have the “why we have these rules” chat too, it actually helps more than you’d think. 
If you don’t want to root, the most “workable” approach is using a DNS-based blocker (or a managed-family app) so traffic goes through a filtering layer she can’t easily bypass—most “app blockers” fail because kids just switch browsers/VPNs. In that thread’s situation, I’d strongly consider mSpy because it supports real monitoring + web filtering beyond basic SafeSearch, and it’s typically harder to circumvent than lightweight block-list apps (though no setup is 100% if she gains enough device admin/VPN control).
Quick reality check: on non-root Android, the main bypasses are VPN/proxy, changing DNS, and switching apps, so whatever you use should also address those, not just block URLs.