Ahead of his State of the Union address, President Obama was in Knoxville, Tennessee, Friday where he proposed making community college tuition-free for millions of students who keep their grades up.

Obama first announced his plan Thursday evening aboard Air Force One in a video posted exclusively to the social networks Facebook and Vine.

In short, Obama wants states to waive tuition for two years of community college to students who maintain a 2.5 grade point average and make “steady progress toward completing their program.” Under the plan, which is modeled after the Tennessee Promise, students would be able to earn the first half of their bachelor’s degree for free. The federal government would cover 75 percent of tuition while participating states would cover the remaining costs.

“It’s something that we can accomplish, and it’s something that will train our workforce so that we can compete with anybody in the world,” Obama said.

On average, the White House says the plan would save a full-time community college student $3,800 in tuition. It’s unclear how many students would qualify, though, and how much the program would cost. Depending on how many states opt in, The New York Times estimates the price tag could reach $15 billion annually.

So far, reactions from higher education observers and lawmakers have been mixed.

"It's bold and exactly what we need right now," Sara Goldrick-Rab, a professor at the University of Wisconsin-Madison, told NPR's Claudio Sanchez. 

In Massachusetts, the state's new governor Charlie Baker said he will review Obama's proposal with education stakeholders "to consider the educational as well as budgetary impacts it would have on the commonwealth."

Skeptics, though, say Obama’s plan is too ambitious because the federal government can’t control tuition costs at state community colleges.

"The right way to expand Tennessee Promise nationally is for other states to do for themselves what Tennessee has done," said Sen. Lamar Alexander, chairman of the Senate education Committee.

In a statement, Alexander said states rather than a federal program should cover the cost:

The reason Tennessee can afford Tennessee Promise is that 56 percent of our state's community college students already have a federal Pell grant, which averages $3,300 to help pay for the average $3,800-per-year tuition. The state pays the difference - $500 on average. 

Obama’s plan, which he will detail in his State of the Union Address later this month, requires congressional approval, and the Education Department has acknowledged that it is unlikely to clear the Republican-led Congress.

You can follow responses on Twitter with the hashtag #freecommunitycollege.