Learning is the process of people explore and develop their way of thinking and also behaviour. Learning new things is also important for people. They need some things that support them to explore and support their process of learning. The process of building a new knowledge needs skills, belief, concept, and also prior knowledge that can help them to familiarize with their environment. Some people said that in learning a new topic or a new concept teacher has an important role to help students build their undertanding about this topic. However, prior knowledge also as important as teacher’s role in helping students deal with new topic. In this paper, I would like to consider the concept of student’s prior knowledge and the important of assessing student’s prior knowledge before studying.

Learning process is the process which personal ideas or meaning is constructed and involve students’ prior knowledge and also experiences (Tytler, 2004). In learning process, conceptual learning related to the concept of developmental stages of children’s cognitive development (Tytler, 2004). It was developed by Jean Piaget. Many books and papers explaining about learning area have been written by him. He has an enormous contribution to educational research. There are four stages of cognitive development namely sensory-motor (birth to 2 years), preoperational (2 to 7 years), concrete operational (7 to 11 years) and formal operation (11 plus years) (Novak, 1978). In each step, Piaget was successful to describe the way children develop their cognitive domain. Although learners now can reveal different types of thinking in different context, Piaget’s ideas about the stages of cognitive domain of children thinking guide us to know that learners might be able to do some kinds of things that depend on their age rather than their skills (Goos, Stillman, & Vale, 2007). During the late 1980s and 1990s, these views were introduced as the constructivism.

Generally, constructivism is a practical idea which considers students as an active learners in the meaningful and essential process of learning and interpretation is important process to facilitate students in constructing their understanding (Cobern, 1993). In constructivism view the process of creating or inventing knowledge is an active process rather than a passively received process. (Booker, Bond, Sparrow, & Swan, 2014). In addition, to help students construct their individual knowledge, learning process may involved social processes such as discussion, argumentation, justification, and negotiation. Developing and constructing their ideas will not be able to be realized without good interaction with other students, teachers, and also their environment. In this way, teachers have very important and essential role because they can help students to improve their skills and build more powerful constructions as well as to develop their self motivation.

In the process of constructing a new knowledge, the successful learning outcomes also comes from the knowledge that learners or students have (Cobern, 1993; Curcio, 1981; McComas, 2014; Novak, 1978). They have this existing knowledge either from their experiences or learning environment. Existing knowledge or prior knowledge is not necessarily a product of formal education which means that it comes from the learning process in the classroom. However, it could be come from student’s experiences or individual exploration (Bransford & National Research, 2000). A case in point is some students have information or know something because they have visited some places or because they have experienced a traumatic condition or even their parents work in particular places. Using prior knowledge in introducing and explaining new topic to students is important part of learning process which teacher should be more concerned about. The important of prior knowledge will be described as follows.

Firstly, a lot of studies talk about that prior knowledge affects how the students perceive and organize new information (Curcio, 1981; Guo, Yang, & Ding, 2014; Matsuka & Sakamoto, 2007; McComas, 2014; Resnick, 1983). In learning process when teacher start the activity with terms and concepts, every students will have many various interpretations based on their existing knowledge either from their previous studies or experiences. Cobern (1993) states that prior knowledge can affect interpretation and interpretation is supported by discourse. As was pointed out in the cognitive development stages of Piaget, the different interpretations may occurs in every stages. Interpretation of new things depends on student’s mental schema. The existing knowledge that students have in their mental schema will help students to intrepret new terms and can build their understanding of the topic discussed. As the result, new information will organize well in their mental schema.

Secondly, prior knowledge also affects how easily students make connections for new information. In the process of learning, students will find lot of new information and therefore existing knowledge can help them to hook up with information that they achieve. They can connect every single information, which is of course appropriate, that already exists in their memory to the new information. The more connections, the easier it is to remember. For instance in studying the concept of fraction, students who have better basic knowledge in proportion, least common multiple, greater common divisor, multiplication, and some other concepts will be easier to undertstand fraction and any operation in fraction. This is why the meaningful process will come when students can connect their previous knowledge to the new knowledge.

Furthermore, in particular subjects, for example mathematics and science, prior knowledge can also help students when they are working with examples (Rittle-Johnson, Star, & Durkin, 2009). Examples can improve students’ skills in problem solving. Appropriate prior knowledge can assist students to understand and compare some kinds of examples to solve mathematical problems in order to estabilish their critical aspects (Guo et al., 2014). In fact, students without existing knowledge will find difficulties in dealing with the tasks given because they must complete some new information before solving the task, whereas the students with appropriate prior kowledge can easily solving the task without overloading their working memory. Rittle-Johnson et al. (2009) in their study of investigating the influence of prior knowledge in using solution methods carry out the effectiveness of comparison in learning equation found that students with lower level of prior knowledge tent to understand examples step by step. By contrast, students with higher level of prior knowledge tend to understand and investigate the number of solving methods. Solving mathematical problems needs students’ skills in dealing with multiple ways to find the solutions. Therefore, students who bring their existing knowledge into the mathematical problems will easily understand and work with the possible solutions.

As have to be remembered that prior knowledge is not only neccessary for helping students exploring new topic but also it can be problematic as well. This is because, the prior knowledge which students bring into classroom cannot be guaranteed whether it can make learning meaningful or not. For example when students learn about how to measure length of objects using ruler, students consider that the lenght of this object can be representated by looking at the numbers in the ruler. The problem is that when they have to use the broken ruler, which the number is not started from 0, some students still use the same way and look at the number in the ruler. They do not recognize that their concept of lenght is incorrect. Owing to this, teachers as the facilitator in learning activities should guide students with their various prior knowledge by giving some instructions. The role of teacher is to help students construct their ideas by solving the problem using their existing knowledge and make the classroom as the best place for them to explore new information, negotiate path to find the solutions, reflect on what has happened (Booker et al., 2014). Teachers will need to ask questions that challenge inappropriate ideas and generalisasiton, and create new problems that may help students to revise their previous constructions or ways of thinking. As have mentioned above, they are a guide as well as motivator to students. However, this is not an easy task to do because they have to deal with the students’ different condition in the classroom. “The challenge will then be to lead children to come to understand and accept this as a method of their own, rather than simply practising and acquiring by rote another person’s way of doing something” (Booker et al., 2014). Therefore, competence teacher needs to be a good guidance for students.

Another example of learning activities that show the important of using prior knowledge to help students successful in learning activies as well as teachers in improving their teaching quality is in topic of measuring angles. Teachers can guide students to understand how to measure angles using nonstandard units before using the standard units. They can start using something from students’ daily lives because it can make students more interested in doing the learning activities. Moreover, their prior knowledge also can come from their daily experiences. In teaching measuring angles teachers can use context of pizza (pizza pictures) as the starting point. Slices of pizza can be used as the nonstandard units to guide and introduce students about how to use standard units for example protractor. An angle measure constructed from a circle of pizza is helpful. Teachers can create some angles shape from pizza for example 90^{0}, 30^{0}, 45^{0} and other angles and use them as nonstandard units. Students should have prior knowledge about kinds of angles and use it to build their understanding of measuring angles using protrator. By doing some meaningful activities using the context of pizza supported by their existing knowledge about angles, they will have a deep understanding of how to measure an angle using protractor as standard unit. In addition, teacher’s role is very important to facilitate students when they discuss and build their undertanding of this concept.

In conclusion, meaningful learning process can be started from constructing students knowledge. The idea of constructing knowledge that generally known as constructivism is developed based on the Piaget concept of developmental stages of children’s cognitive development. Constructivism looks learning process as the active process of creating knowledge. Constructing a new knowledge can be developed from knowledge which students have and bring to the classroom prior to commencing a new topic. Prior knowledge or existing knowledge might be coming from student’s experiences or their environment conditions. It enable to help students to accept, organize and connect the new information during the learning process. In adddition, prior knowledge can help students in comparing examples. However, the role of teacher is still important to guide and facilitate students develop their new knowledge. In the future, teacher should be more concerned about the prior knowledge of students and be more active to guide students in constructing and dealing with the new information. Teacher will be the main facilitator and also motivator for students in learning process.