As a teacher, your class will take its lead from you in all that you do. The use of language is the first place this will start. Your example of using the language of the subjects you teach must be at the highest possible level. That doesn’t mean to use words whose meanings are not known to the class but rather ones which enhance a child’s progress.
Obviously, any new terminology you use in each subject must be explained and used in ways to consolidate the new work to be learnt. Below are some ways you could enhance the students’ understanding of the use of language.
Colourful language. This does add interest or excitement to what you say or teach. No one says that when you teach you must use boring language. Use words that add colour and excitement to what you teach. Make it a goal of yours to look for ways to add colourful language particularly to the more difficult topics that you teach.
Use the language of the subject discipline often. Teach the class the origin and meaning of each new term that you introduce.
Create a spelling list of terms as you teach each topic. Some texts provide the lists for you.
Have a quiz of these terms often. Have little spelling bees/contests.
Have what I might call a definition test/quiz where the students write a definition of a subject term in simple language to explain its meaning to a person who has never seen the word before.
In your own speaking, learn to say the same ideas in as many ways as possible to give constant examples to your class about how to use our language in a variety of ways.
Insist that your students use the terms of the subject discipline in their answers to questions they write and in the questions or answers they ask or give.
Many modern syllabuses contain a requirement that communication as a skill in the subject must be assessed as part of the total assessment program. This implies that the student must use the terminology of the subject in their answers to all assessment tasks to show understanding of the language of the subject being tested.
The student needs a good base in the language of the subject to know what is required in each assessment task before they can begin to answer the question and answer in such a way as to show understanding of the subject.