Echo voice even headset is used

hello
we are from India , we are using jitsi meet for conducting classes some students using android phone and headset and some using laptop with headset

every time two or three students can face echo problems not all times somewhere in between running classes (just i told them do not use phone speaker) even they all using headset they hear echo voice , but i am not getting echo as iam using laptop and they all using app

kindly please suggest me

thanks
praveen
lecturer in CS