Yes, it is useful for the students in secondary levels to have smartphones because they might need it for distance comunication with friends/ even family... they can also so be useful when it comes to online learning especially when we are in lockdown and to upload and revise...
But if u think about it, there is lots of bad things that happen on the internet and social media... kids/teens are too young to understand or experience what adults know already or experience... and all this that happen, is all because of the phone. if it weren't the phone, they will be no way they wil be able to comunicate to strangers on social media or even have the ordercity to meet up with that stranger... thats why smartphones might be toooooo risky for kids/teens........