WASHINGTON — When Democratic Rep. Mark Takano got his hands on a draft letter to Speaker John Boehner from conservatives on immigration, he did what any pro-reform member of Congress who was a high school literature teacher for two decades would: took out his red pen and marked up the draft.

Unsurprisingly, he gave the Republican letter an "F."

"If you don't understand the bill come by my office and I'll explain it," he wrote at the bottom in his best teacherese.

The letter, which is being circulated by Louisiana Republican Rep. Bill Cassidy and is addressed to Boehner, is a rebuke of the Senate's comprehensive immigration reform bill. It includes complaints that the Senate bill is "over 1,000 pages long" and was created in a "secret and underhanded way." Cassidy's letter calls on the House to reject a comprehensive bill in favor of several smaller bills targeted at specific immigration arguments, like border security.

The signatories of the letter are a Who's Who of Republican comprehensive reform opponents in the House, including Reps. Tim Huelskamp of Kansas, John Culberson and Mike Conaway of Texas, Charles Boustany and Rodney Alexander of Louisana, Steve Palazzo and Alan Nunnelee of Mississippi, Joe Pitts of Pennsylvania, Tom Price, Paul Broun and Austin Scott of Georgia, Paul Gosar and Trent Franks of Arizona, Andy Harris of Maryland, Doug Lamborn of Colorado, Jeff Duncan of South Carolina, Bob Latta of Ohio, Michele Bachmann of Minnesota, Blaine Luetkemeyer of Missouri and Richard Hudson of North Carolina.

Outside the White House Thursday, leaders of the Senate Gang Of Eight, which authored the immigration bill, rejected similar complaints made by conservative Republicans in the past.

"Those extreme opponents, they keep coming up with new reasons to oppose the bill. One of their latest is, 'oh, our bill is a thousand pages and complicated,'" said Sen. Chuck Schumer, a Democrat from New York. "Well, from what I understand, the bills they are putting together -- and they only have half of them done -- are already 500 pages."

"It's what in those pages that's important, and what's in those pages is supported by the American people overwhelmingly -- Democrats, Republicans, business, labor, the whole religious community," Schumer added.

Takano's office says the marked-up version of the letter, which staff posted to both Takano's Facebook and Tumblr pages, has been a hit. After about two hours on Facebook, the letter had already been shared more than 1,000 times.

Update: In a statement, Cassidy responded to Takano's edits.

"Representative Takano's action and grandstanding represent everything Americans hate about Washington, but I won't let his partisanship stand for all of us," Cassidy said. "My colleagues and I are absolutely going to keep requesting that the Speaker listen to the American people, not the big money interests and rank partisans trying to bully and intimidate members of Congress to quickly pass this massive amnesty bill."