In regards to Science Instruction, it is extremely important to use Formative Assessments. As a teacher you always have to ask yourself if what you are teaching 'follows the curriculum' and if you are using Formative Assessments, it will be easier as a teacher to keep track of students learning. As you're working through a unit, assessing after every part of the lesson even if its just an exit ticket is important in keeping up with where the class is and if everyone is on the same page.
Formative Assessments are designed around what you want or need students to take away from a unit or lesson. You can use Formative Assessments to also give students the opportunity to ask questions about things that are un clear.
There are Pros and Cons of both Summative Assessments and Formative Assessments. Love Joy Amargo, Teacher at SJIDI shared many pros and cons for Summative Assessments that I highly agree with.
Dr. Nesa Sasser, studio D writes advantages and disadvantages of Formative Assessments in her article What are the Advantages & Disadvantages of Formative Assessments. A pro of Formative Assessments is the fact that they are not graded, which takes the anxiety away from students. It also eliminates the idea that they must get everything right. Another pro is that they serve as practice for the students and allows them to assistance and immediate feedback from the teacher along the way before the 'big test at the end'. Another Pro is that teachers can check for understanding in the event that students are struggling during the lesson. Teachers address these issues early on instead of waiting until the end of the unit. Teachers also have to do less re-teaching in the end because many of the problems were worked out and addressed before the final test.
A con for Formative Assessments for many teachers is sacrificing time to assess during the lesson and fear that they may not even finish the lesson. Time is a evil thing that teachers fight against every single day. Another Con is that teachers may feel the need to rush through a series of units when they feel that they are pressed for time, which causes students to lack mastery once the assessment is given at the end of the unit. Knowing that Formative Assessments usually have little to no point value unlike Summative Assessments leads to the last Con I can find with Formative Assessments, "students may not take the assessments seriously, which may cause teachers to misread feedback from students".