Schools Chancellor Joel Klein says summer school enrollment is expected to double this year.

In a wide-ranging interview Thursday on NY1's "Inside City Hall," Klein says based on the belief that state grading standards are tougher this year, more than 20,000 elementary and middle school students will likely be required to attend summer school next month.

Klein says that the city will not have a complete picture of test results until July, but he’s making a conservative estimate of how many children failed the state math and English tests.

"We have to make promotion decisions, so what we did is take a hard look at based on what we are hearing which is that the changes of where the scores will be, not in terms of performance, but where you make your cuts, we may be looking at more students at level one," Klein said.

If the state goes ahead and uses a tougher standard for scoring those tests, that won’t just affect summer school. Students could see lower grades while teachers could end up getting harsher evaluations.

In recent years, students scores have shot up on the state's English and math exams, but not on national exams. As a result, state education officials began to realize their exams may have gotten too easy. So this year they're making it harder to pass. For example, while seventh graders only needed to get nine out of 41 questions right on the English exam to pass last year, this year the city thinks they need to get 22 out of the 41 correct.

"We have a broken system but we know, I believe, we know that's its broken and that's the first step to fixing it," said State Education Commissioner David Steiner.

Even with 11,000 more students being sent to summer school, the DOE says it won't open any additional sites.

Last year, summer school cost the city $53 million.

"We have the budget, we have reserved enough to address that, so I think this is a sensible move," Klein said.

Meanwhile, the chancellor also spoke about a lobbying trip he made to Albany this week with Mayor Michael Bloomberg and teachers union president Michael Mulgrew to urge state lawmakers not to cut the city's education budget.

"We are 40 percent of the state here and we've got over a million kids in schools and those million kids deserve to have their representatives in Albany to act in a timely and responsible manner and I expect they will," Klein said.

On the contentious issue of teacher salaries, Klein says that any hope of a contract with the teachers union could be a long way off.

"One party is looking for four-and-four and the other party has offered zero-zero, that's not a close place. But as far as we are concerned the current contract which expired, is one we live under," Klein said.