Consider the exam class. In the example below, comment or uncomment the \printanswers command to replace the ruled space for a student to write their answers with your own typeset content. No problems with questions spanning multiple pages, either.
\documentclass{exam}
\usepackage{lipsum}
%\printanswers
\begin{document}
\section{Questions}
\begin{questions}
\question[10] Why is there air?
\begin{solutionorlines}[1in]
For several reasons.
\end{solutionorlines}
\question What if there were no air?
\begin{parts}
\part[5] Describe the effect on the balloon industry.
\begin{solutionorlines}[0.5in]
Bad.
\end{solutionorlines}
\part[5] Describe the effect on the aircraft industry.
\begin{solutionorlines}[0.5in]
Worse,
\end{solutionorlines}
\end{parts}
\question[20]
\begin{parts}
\part Define the universe. Give three examples.
\part If the universe were to end, how would you know?
\begin{solutionorlines}[1in]
Something else goes here.
\end{solutionorlines}
\end{parts}
\question[60] \lipsum
\end{questions}
\end{document}

exercisepackage. – cgnieder May 15 '12 at 12:55