Shanti, DS1 was the same from about 12 months. I think he didn't feel part of the family sitting at the table while in his highchair. We bought him a Phil & Ted's Me Too seat which attaches to the table and he loved that. It was more like he was sitting at the table with us. DS2 never actually used a high chair at all - just the Me Too seat.

Now the boys are bigger we have bought them bar stools which actually look almost exactly the same as our dining chairs, but higher. They sit in those at the table and it works really well.