State school board members threw their weight behind proposed legislation to tighten smoking rules in schools and deter adolescents from taking up the habit.

The board agreed to support legislation being sponsored by Rep. Kim Burningham, R-Bountiful, and Rep. Hugh D. Rush, D-West Valley City. The bill would make 21 the legal age for purchasing tobacco products and would increase penalties for those who sell such products to underage individuals.The bill also would ban smoking from school buildings and grounds during hours when children are present as well as confining it to designated smoking areas at other times.

The sponsors hope tougher laws will send a strong message to youth about the health hazards of tobacco use, Brad Nieger of the State Health Department told school board members Friday.

Board members suggested only that restrictions should be even tighter.

"Why allow smoking on school properties at all?" asked Board Member Keith Checketts.

Rush said the bill's sponsors believe it has a better chance of passing if it allows for restricted smoking than if it banned it entirely. He said he expects the measure to be very controversial during the 1989 legislative session.