vkartikv said:
Am I silly in trying to impose this on a 11 yr old beginner?
Yes, unless this child is already very athletically gifted.
My son started playing tennis last year, also as an 11 year old. He was a 5' tall, 110 pound 11 year old, with four years of little league baseball and two years of weight lifting behind him. He still needed two hands on the backhand, because the tendency was to rotate the body and drag the arm along with it, resulting in a side-spinny shot that had an outside-in racquet path whenever he was rushed. This shot is almost impossible to time well, and I remember thinking this was really pretty reminiscent of the backhand of Jimmy Arias, which I recall looking rather uncoordinated. With two hands on the racquet, the trunk over-rotation problem went away.
There are many problems with kids playing at the net. One is that larger racquets allow easier topspin, and even if the shot is not over their head, it is hard for younger kids to have the shoulder strength to hit a head-high shot when they have to stretch for it, and especially so on the backhand side if one-handed. The second is that it is very easy to get a shot over their head, and moving backwards is not a skill that's easily learned. That's not to say you shouldn't teach them this aspect, but don't make it the staple of their game or they will get very frustrated.
Just let the child determine how they want to play. If they have a lot of determination and are willing to sacrifice some short term shot-making ability for long term gain (something that is VERY difficult and rare for kids to do), then you can start teaching them the proper way to execute shots, including grips, swing patterns, etc. Otherwise, just have them concentrate on good footwork so they can get to the ball, and let them swing away until they get a good feel for how the ball bounces and how they need move. That'll be more exercise, more fun, and if/when they get hooked, they'll have a good foundation.