Thirteen health and community groups sent Gov. Bob Mc­Don­nell (R) a joint letter Tuesday urging him to sign a bill approved by the General Assembly that would require public elementary and middle schools to offer students 150 minutes of physical education a week, raising pressure on the governor over an already hotly contested piece of legislation.

The groups, including the Virginia chapter of the American Academy of Pediatricians, the American Cancer Society and the American Heart Association, cite statistics showing that 1 in 3 Virginia children are overweight and the health risks and public medical costs related to obesity. They call the bill “critically important legislation would help make our children in elementary and middle school healthier and more active.”

Mc­Don­nell has been facing an equally vigorous campaign from school systems and local governments, urging him to veto or dramatically alter the bill. They say it is an unfunded mandate that would cost schools millions to hire new teachers and take time away from other subjects, including art and music.

In their letter Tuesday, the health groups note that the legislation, which was sponsored by two doctors in the General Assembly, would give school districts until the 2014-2015 school year to implement the change.

Mc­Don­nell faces a difficult choice with the bill. He has long opposed new mandates for school systems. But his administration has also prioritized reducing childhood obesity in a public education campaign led by his wife Maureen.

The bill received bipartisan support in the General Assembly, where it passed the senate 38 to 2 and was approved by the House 55 to 40. If support is bipartisan, so is the opposition, which includes leading Republicans like House Speaker Bill Howell.

Mc­Don­nell has until March 29 to decide whether sign, veto or amend the measure.