need advice on phone for highschool kids

doctorman Yes, all options are pretty pricey for dumbphones, but that's what there is available nowadays. The Sunbeam is somewhere in middle at around $190.
Im pretty sure if you want some apps such as waze you can still get a one time fee filter, I don't know about MB Smart for free, you'll have to ask TAG what they have. (To be clear, this is for the s22, the FIG and Sunbeam phones are pre filtered and only come with limited apps, and cannot be added by the user)
The F21 and the F30 are the same phone, but the F30 was supposedly modified to have better bands for the US carriers. I would stay away from the F21, the reports im getting from people is that it has terrible service on T-Mobile. I think the F30 is better, but I don't know of anyone personally who has it.

The kyocera dura xv you can buy brand new on ebay for 160 or like new for about 100 and they last usually for a few years so its a good investment and the only secure filter is one that a organization like tag or meshimer etc puts on for u because if u remove the browser via ADB it can be restored by resetting the phone besides for the fact that almost any app can be added to the phone and be hidden well too, for the Kyocera u can use us mobile which has unlimited talk and text for 14 dollars a month. Regarding the sunbeam, in my opinion, DO NOT BUY my wife had it and I had it replaced by warranty and the second one broke too kept on crashing and very not sturdy phone a other option is LG classic which tracphone has refurbished for $15! but its locked to tracphone for 12 months and after like 6 months or so the keypad becomes blown up and it becomes hard to type and their service is a little expensive $25 a month for talk and text and I think 1 Gb of data and that phone can be filtered as well

For T-mobile (or Tello which is the cheapest service provider I think, and they have international calling free to 60 countries and they run on T-mobile) you need a gsm volte-voice over lte compatible phone which there aren't any great options in flipphones that are volte compatible the schok phone me and my wife had it broke almost right away and the warranty didn't get me anywhere there is the nokia 225 which tag can filter and it costs around $50 but I don't have any info how good of a phone it is, the sunbeam as I mentioned earlier is extremely junky and not reliable keeps on crashing and breaks easily and very not sturdy needs better firmware and to be made more sturdy built, the NUU phone is less then $100 and it is volte compatible and is also cdma compatible BUT it is EXTREMELY slow and u have to wait like 2 seconds after u press a button something should happen and as I use to say when I had it that on top of all its problems it also has the fault that it comes with whatsapp built in to the phone

doctorman They both run android but are both securely blocked, even with ADB.