Some people think the _______ problem at present is how to m

Some people think the _______ problem at present is how to make the students develop
Some people think the _______ problem at present is how to make the students develop by themselves(education)
为什么这里用education,而不是educational
请详细说明,谢谢
一般名词前都是形容器修饰，为什么要用名词
请高手解答