Air Conditioning - Hot rooms

I have another thread which is seperate from the other issue. As stated we moved into this house 3 years ago we were the first and only occupants. From day 1 the AC upstairs only seems to cool the master bedroom very cool. My sons room is on the front of the house and his room is like a sauna and the master bedroom is like an ice box. there are 4 bedrooms upstairs, the three auxillary bedrooms use the return exchange which sits in the hallway, so when the children close their doors their rooms get extremely hot. One of the ac technicians suggested placing return exchanges in each room. would this assit in cooling the rooms? would this also take away any coolness from the master bedroom since there will now be 4 return vents as opposed to 1? what would be the best way to cool the rooms if adding the return exchange is not the best method. thanks

undercut the bottoms of the doors

so undercutting the bottom of the doors as opposed to adding return vents should take care of the problem?

Both will work! Under cut about 3/4 inch is all that is needed.

thanks I will try this and let you know results