My college teacher gave us a brainteaser for elementary kids and I can not figure it out!

next letter: s,m,h,d,w,m,_?

ok
seconds, minutes, hours, days, weeks, months, ?? then what?

next is years

years?

Ok, yes. Years is the next term in the sequence I gave, but the letter "y" should be the next term in the sequence that the poster asked about.
Got it?

the next letter is h