The alternative I went with, and which I recommend, is getting both a smartphone and a nokia shitphone (no internet). Then ask the carrier for a sim duplicate. These exist, and are in fact a new number that redirects to your number. Use and carry whichever you want, knowing that calls will all go to both phones.
There is always the peer pressure excuse but thats not good enough. At the end who buys and setups and keeps paying for that phone?
Back in my day (when we walked to school uphill both ways), we weren't allowed to carry around basic flip phones. They had to be in our locker and only used before or after school.
When and why did it become acceptable for much more distracting and stimulating devices to be allowed in class?