Honestly, a basic flip phone still works fine on most networks — I got one for my 10-year-old for the same reason, but I also put Eyezy on it so I can see who he’s contacting during my night shifts when I can’t be there to check in myself. Gabb Wireless and Ting also make kid-friendly phones with no apps or browser if you want something more purpose-built.
Check out Eyezy here: