Emily asks for my perspective on flashcards and worksheets.
In general I can say that I don't ask kids to read words in isolation. A study I'm trying to track down for you showed that kids can read 60% more of the same words in context (with the support of all the cueing systems: phonics, meaning, grammar) than they can in isolation. Words in the real world are always part of texts, not apart. (Even STOP on stop signs is always in white print on a red octagonal field.)
One day I walked by a mom who volunteered for a first grade teacher by monitoring kids reading "sight words" on flashcards. One kid correctly read the word "were," to which the mom responded, "Good reading! Here's your sticker!" At the same time, the kid was quizzically shaking her head, "Were. Were. What's a were?"
That being said, the occasional flashcard isn't going to hurt a reader. Rather, I would question how much they actually help. I prefer to focus on kids reading real texts.
Another study quoted to me by a prof in grad school documented that 80% of the spelling errors kids make after grade four are usage errors, like there for their or they're, or personnel for personal. It is not possible to spell these words correctly out of context, so all the more reason to focus on writing, and then edit for conventions (spelling, punctuation, grammar) in the final stages.
It's hard to comment on any particular worksheet outside of seeing it. In general, worksheets require a minimum of writing on kids' part, especially in the early grades. An entire piece of paper may be used for a child to draw lines between 5 words and 5 pictures, or to X several boxes. These pieces of paper have such a short life, and classrooms where lots of worksheets are used are often littered with them, or one can likely find many of last week's worksheets crumpled up in desks. (Corrected, or completed but not turned in, or incomplete: Which is worse?) Moreover, many worksheets must be almost incomprehensible for kids, as adults can be challenged to figure out what is being asked.
In contrast, many of the purported goals of these practice sheets can be accomplished in spiral notebooks or composition books, and the more kids write, the more evidence of their understanding, as well as their growing skill as writers. Midway into my career I made a goal to use no more than one sheet of copied paper, per kid, per day. On most days that was a group-authored class newspaper on one side, and something relevant to our current learning on the backside. The kids eagerly read their news, and the parents counted on the Notes for Home section to keep them updated. All other draft or informal writing was accomplished in 19 cent spiral notebooks from someplace like Target. If the purpose of the writing was not obvious and it was important for parents to understand my intentions, I ran off small notes describing the assignment that we glued right on the page.
Emily's question touches on trends in "best practices." Here is a web-based adaptation of the work of Zemelman, Daniels, and Hyde: Best Practice: Today's Standards for Teaching and Learning in America's Schools. (I prefer the earlier first or second editions.) Both include worksheets ... decreasing in use.
Trust your judgment on their value. And ask yourself: "What are my most valuable learning experiences? What have I saved in a portfolio or box of artifacts?" If you answer a worksheet, let me know!