What method would be ideal to teach photosynthesis for class 5 to 8 students?

take them outof classroom and show them naturel expérience

Demonstration, i.e., depending on the best availability of resources, you can,

Show them in class using artificial light or

Take them outside, as the natural process is the best way to see the process clearly. 

, students show difficulties in understanding photosynthesis and respiration, and basic ecological concepts like energy flow in ecosystems.
There are successful teaching units accomplished in this area and many of them can be described as inquiry-based teaching.
One definition of inquiry-based teaching is that it involves everything from finding problems, investigating them, debating with peers and trying to explain and give solutions.
Accordingly students need to be confronted with challenging questions and empirical data to reason about and teachers need to implement student-generated inquiry discussion since students often stay silent and do not express their thoughts during science lessons.
This thesis will focus on young peoples’ understanding of the functioning of plants, students’ participation during biology lessons, and how biology teaching is accomplished in primary and secondary school.

Photosynthesis doesn't happen indoors. Therefore it would make much sense to take them outside to discover for themselves (of course with your supervision and guidance)

ACITIVITY BASED TEACHING METHOD, 

TEACHER PREPARE  EXPERIMENTS, AND   ACTIVITIES, PROCESS OF PHOTOSENTHESIS,

MAIN TOOLS ,    LIGHT+ GREEN TREES+AIR, ............

PROJECT ACTIVITY,