Turn off the TV set
Make it a house rule that when it's homework time the TV is switched off.

Music and radio?
Some children function well with their favourite music playing through their earphones. Others will find this distracting.

Phone calls
Insist on mobiles being switched off at homework time!

Designate specific areas for homework and studying
Possibilities include the child's room or the kitchen or dining room table. Eliminate as much distraction as possible. Most children's desks aren't big enough to spread out materials. A table with enough space for all their equipment works better.