which form should i use in this sentnce?
I will study the textbooks at the secondary , the high school , and the pre-university levels for a college entrance exam.

OR
I will study thee textbooks the secondary level , the high school level , and the pre-university level for a college entrance exam.

Question

which form should i use in this sentnce? 
I will study the textbooks at the secondary , the high school , and the pre-university levels for a college entrance exam.

OR
I will study thee textbooks the secondary level , the high school level , and the pre-university level for a college entrance exam.

Answer

#1.

Answer

For the listing of levels, use "I will study the textbooks at the secondary, high school and pre-university levels for a college entrance exam."  That is OK and clear.

Answer

Since you are preparing for that exam so you have an arrangement for something to do in the future, in such case you should use the form ( be+going / planning to+infinitive )

secondary school = high school 
I don't know what do you mean by( pre university level)