reporter: it is the latest and maybe most extreme approach to curbing a shortage of bus drivers. the national guard are training to transport school kids. it is out of the box. reporter: the superintendent of chelsea schools near boston says two weeks into the year and she s still short 15 drivers. meaning one in every five busses has run late. now the guard will drive ten passenger school transport vans in her district. we ve worked so hard to get our students back. we want our students back on time and ready to learn. reporter: schools returning to in person classes say coronavirus fears pushed more drivers to retire. it is the worst shortage ever say administrators in fairfax county, virginia. the district is paying new bus drivers a $3,000 sign on bonus.