You've received some good responses so far, and I have a few things to add.
First, I've noticed that sometimes children of all ages (even little ones like yours!) will sometimes do for others what they won't do for mom and dad. I'm not sure why this is, other than maybe it's just someone new asking them to do something/try something new.
Also, I'd ask the day care not only WHAT they are feeding your little guy but HOW MUCH he is eating. It's possible he's consumming all the calories he needs at day care, and just isn't interested in solids at home. This may explain why you can get him to eat meals on the weekends but not eat solids during the week. If he's eating way too much at day care, you can ask them to feed him less so you can feed him more, or ask them to not feed him new foods so you can introduce them to him yourself, etc. They should be willing to work with you on this.
One other thought. Children, especially infants, can pick up on our stress, even if we try to hide it from them, so if you are very stressed about your son not eating solids, he may be picking up it, and the stress may be affecting his eating. If you think this might be the case (and I'm not saying it is, I'm not there so I don't know!) you might try and relax while you feed him and see if it helps any. Maybe you could sing to him while you're feeding him, or maybe have some music inthe background...or find some other way to make eating a little more fun/distracting for him.
One more thought. It's possibe he is developing an ear or sinus infection, is he showing any signs? If so, you may want to have his pediatrician check him out.
Good luck!