I do think taking away those things was good, but NOT as punishment, I just think they may be contributing to his lack of love of learning in general. You DON'T want to get into a punishment cycle on school work, or he'll hate it all that much more, but you DO want to nurture an environment in which it is natural, easy and interesting to study. I know your son is bright by his early achievement and luckily his failings are just starting so it's not too late...I don't understand how he got on honor roll first semester already? Do you mean last year?
This is not meant to be critical at all, it's only addressing the fact that he is not focusing properly on school work in studies that may not interest him (very difficult to do but important to work hard anyway). You mention a play station, ipod, cell phone and TV in his room. That is a LOT of electronics for a 4th grader. I know it's fairly typical these days, but I wouldn't have done all my school work either with all those screens taking up my time. Plus those mediums BREED lack of concentration and focus. His mind is in a passive state when wathing TV (even educational) and learning is not as deep on the electronic gadgets because your mind isn't forced to create the visuals it needs from text etc. It's much easier to "watch" colorful graphics than to imagine things. And it sounds like his concentration abilities are suffering if he's forgetting things and being lazy.
I'm not saying he should never do any of those things, but it would be more conducive for his study habits to NEVER have a TV in his room, but have limited TV time with family. He doesn't need a play station or ipod. Those are luxuries. The cell phone depends on what your families schedule/safety needs are, but meh, if it has games and texting and other other ways to distract himself, you could limit it to just calls.
My oldest is only in second grade, but she has yet to have ANY electronics and won't have any until AFTER 4th grade even for learning. She has always only had access to books and paper and crayons and limited TV watching, some games in waiting rooms if her friends share, etc. As a result, there was nothing else for her to become but a really good reader who loves to draw or build with legos etc, and she's got great concentration for her age from sheer practice. Also, we've always made educational books part of fun reading, so she's used to "enjoying" educational books, studying for tests etc. She can read a difficult history chapter and take a test on it all on her own. The key is keeping it FUN and keeping the distractions limited. If she doesn't feel like reading or drawing or building, she can play outside or with dolls, but she has to use her mind, not check out on a screen. I know my attention span has suffered as I've increased use of a computer and children's minds are just developing.
If your son feels like all his electronics are the "rewards" for doing the bare minimum of his school work (passing), then it doesn't seem like a recipe for long-term success. Can you remove most of them permanently, but leave TV in the in shared room for some enriching movies or shows on a limited basis, and then start doing some fun activities together that incorporate the studies that he's not showing an interest in? What is he studying in social studies? How does it pertain to life? Are there activities you could do together and point out in a non-pressured way how the real world relates to what he's learning? We're studying medieval times right now, so this week we're sewing some renaissance gowns and heading to the Rennaissance festival. That's kind of elaborate, but sometimes we do normal errands and I'll relate it to the news or get a fun library book about a mundane topics so the kids can hear about a "lesson" a few different ways at different times to set it in.
If you get into ways to help the studies become more interesting, AND give him a little TV to unwind, AND set up a special reward for a certain amount of achievement, like a special day trip with him or something after x amount of successful school weeks, those might be some ways to help. You want him to love learning, not HATE school.
And I would make the electronics disappear for good and he just has to accept he doesn't have time for playing with those when he's not managing to learn things that are important to his life. Maybe he can have them back in the summer if the grades come up this year....but I would lose them personally. You're them mom, he's not ENTITLED to electronics that suck away his time and attention span unless he shows he can work hard in school AND play those in his left over spare time.