I've moved towards the "I can" statements, as that's what the school district is moving towards. At my last school, my teammate and I added "I can"..., "So I can...", "I am successful when..." Students respond well to that because they know WHY they're doing what they're and how they'll know when they're successful. I think when and how you use them is dependent on what you're doing. There are absolutely times students should be told what they're doing and why they're doing it. There are other days we go through the lesson and I ask them what they think the target was, which can be pretty eye-opening. Because of my job, this year my plan is to focus on more on what can be referred to as "Habits of Learning": I can solve math problems in more than one way I can communicate how I solved the math problem I can ask for help when I need it I set goals and monitor my progress towards my goals I can use more than one strategy to understand what I'm reading Those are super generic, but that's the direction I'm heading.
If you have time and are interested, I'd suggest reading Leaders of Their Own Learning. At the very least, the chapter on learning targets. It's easy to post the objectives (which is often all schools want to see), but it's a little more difficult to incorporate them in ways that matter to learning and students.
I type a daily lesson goal on my Smartboard (includes what students should take out and their homework assignment to write down). After a few minutes to unpack and write down hw in their planner, I choose one student to read the lesson goal and the agenda steps (that are written on my whiteboard). I might ask students what is the main topic or how they think we will accomplish that learning goal to get their brains warmed up.
Though I'm nowhere near 100% at this, I use "I can" statements that I change out regularly on our board, often in the format "I can ____ -- bigger target --, by ___ -- specific target for the day in a different color --", and then during the lesson intro, as I'm connecting and giving the purpose of our learning, I try to incorporate it in a fashion where it isn't just "Here's our learning target!", but instead, where it fits in organically. For example, "Yesterday, we discovered and became experts at one way of solving multi-digit multiplication. Today, we're going to look at the multiplication a slight bit differently, and you'll discover a second method that can help you solve multiplication problems. By the end of the day, you'll be able to multiply multi-digit numbers by __ and by __". I feel like directly just "saying it" makes it less meaningful, but having a purpose is highly important to direct their learning/attention and so they can assess afterwards and during to see where they're at compared to where they need to be.
We have an essential question for the week printed in our reading textbook. I have a student read that and then we move on. At the start of the year last year, I had students read the objective and write it down every day. I do think they appreciated the focus, but I found it a waste of time, and I don't think that it impacted their ultimate success any more than simply stating at the start of a lesson, "Today we're talking about ___," which is what I do now.
We have to write or post I Can statement on the board for each subject. I used to have student repeat after me the statement at the start of each week. Last year, because of a change in the observation rubric, I also started stating the I Can statement along with howt it related to the year end goal.
Here's an example of what I said during an observation on a long vowel a lesson. "This week we have been learning about the letter A. Today we are going to learn about the long sound that the letter A makes. By the end of the school, year we will have learned about all of the vowels and the sound they make. Because you will know the short and long vowel sounds, you will be able to read more words." We seriously had a faculty meeting g because so many teachers were getting dinged for not tying the lesson's objective to the over all year end goal. And I teach kinder so you can imagine the looks on their faces after that speech.