Late buses plagued the start of school in Boston on Thursday as temperatures climbed into the 90s in thick humid air, causing some students at bus stops to give up in frustration and go home after waiting almost an hour.

Nearly half of the buses were tardy, but 80 percent of all buses arrived within 15 minutes of the opening bell, school officials said. That performance was better than the first day last year when 59 percent of buses were late. But it was comparable with two years ago when 49 percent were late.

The problems came amid negotiations for a new contract with the bus drivers union, which has threatened to hit the picket lines if members can’t secure a fair deal. But Mayor Martin J. Walsh said he didn’t think the two issues were related, and he put in a good word for the drivers.

Read the full article on the Boston Globe website.