MLA format requires in-text parenthetical references.
Can I use footnotes?
Not advised for any year level. IB discourages the use of footnotes. Footnotes and endnotes, if used, do count against your total word count.
"Footnotes and endnotes may be used for referencing purposes and if this is the case will not be included in the word count of the essay. If information is contained in a footnote or endnote and is not a reference, this must be included in the word count. In order to avoid confusion and unwittingly exceed the word limit, students are advised to avoid using footnotes or endnotes other than for referencing purposes unless it is appropriate.
An essay that attempts to evade the word limit by including important material in footnotes or endnotes will be compromised across the assessment criteria. Please note that footnotes and endnotes are added to the word count as they are encountered. ("Footnotes and endnotes").
"As creators/authors, we are expected to acknowledge any materials or ideas that are not ours and that have been used in any way, such as quotation, paraphrase, or summary. The term 'materials' means written, oral or electronic products, and may include the following:
Basic and common knowledge within a field or subject does not need to be acknowledged. However, if we are in doubt whether the source material is common knowledge or not, we should cite!"
from Effective Citing and Referencing, by the IB Programme of International Education, 2014