You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Bill_%26_Melinda_Gates_Foundation

Context:
The K-12 and higher education reform programs of the Gates Foundation have been criticized by some education professionals, parents, and researchers because they have driven the conversation on education reform to such an extent that they may marginalize researchers who do not support Gates' predetermined policy preferences. Several Gates-backed policies such as small schools, charter schools, and increasing class sizes have been expensive and disruptive, but some studies indicate they have not improved educational outcomes and may have caused harm. Peer reviewed scientific studies at Stanford find that Charter Schools do not systematically improve student performance

Question:
Have the policies been criticized 

but some studies indicate they have not improved educational outcomes and may have caused harm