Hi
I put my eldest, Brooke in at bed at 11 months because she hated the cot. It was a junior bed with barriers and i never had a problem, she didn't even get out of it. I think it was because she was so young.
My neighbour put her little boy in a bed just over a week ago now, he will be 2 at the end of this month.
The first night that he was going in it she left him up a little later to tire him out. She put him in it and went down stairs and he got out of it. So she went back upstairs and put him back in an said no its bed time. She did this every 10-15 minutes and eventually he stayed in and went to sleep.
She said he does still get out some nights but others he goes to sleep.
I would just suggest that you do what my neighbour did and keep going up n putting him back in if he gets out, eventually he will realise.
HTH