Teacher's unions fight for sick/personal days during "bargaining". Depending on the public school district, a teacher can accumulate a LOT of sick days (personal days can roll over into sick days up to a certain # in some districts). This teacher may have had a lot of sick days to use up, been able to retire, and used them during this time. Depending on the district, he may get "cut a check" for X amount per sick day not used when he retires. Don't know if that is what dante was talking about, but thought this may help.
Not really sure if the school can take his accumulated sick days away. Common sense may say they should be able to, but guaranteed the union would fight that.