sitting down

For a few days in a row he has refused to sit on the booster seat. We tried to push him in the seat but it is just so hard, he struggled like a man! He climbed up the adult chair and sat there for a little while to eat and then climbed down the floor again. He wants to sit like us, not in the booster seat strapped in. Not sure what to do with him now... the closest thing that i can think of is the Hauck Alpha III High Chair, its like a wooden chair, the seat and foot rest is fully adjustable.