Security camera footage shows 12-year-old and 13-year-old Israeli boys wearing hooded sweatshirts, entering a bank in a suburb of Tel Aviv on Wednesday.
Police said both were carrying fake M-16 assault rifles and shouted "this is a holdup". But they fled without any cash after apparently losing their nerve.
The toy guns looked real and scared people inside the bank, police said. But lawyer Gil Gabay said the childrens' rights were violated.
"We are talking about children aged 12 and 13 who were arrested last night at 2300 (2100gmt). They were investigated during the night against legal instructions. They slept on a chair in the police station. Their rights were significantly violated. I think they should have been treated differently. I don't think they should have been treated like criminals."
Police identified the pair from the security footage and later arrested them.