Is my child immunocompromised or is this normal?

Since attending daycare for the last year, our son(16 months) is constantly sick. He holds a high fever for about 6 days until it finally breaks. But he is always sick. I understand it's the nature of the beast with daycare, and we live in Florida so the climate just breeds the germs, but I thought his immune system would have built up by this point? This week he was sick with an ear infection and the flu, he was on antibiotics for 5 days, but spiked a fever on the last day after he returned to school for 1 day. (This was after 5 days of antibiotics and 2 days of no fever)

Is this normal for kids?

Thanks in advance- an always tired, worried mom.