The Pledge of Allegiance was first created in 1892 to foster a sense of national unity. It was brainwashy even back then, especially having children recite it every morning, but it wasn't really intentionally malicious. It was intended to instill a sense of national fraternity in a fractured group of people, during a time that political tensions ran high and America was being filled with a large percentage of immigrants. Giving everyone an identity as Americans was important in moving the country forward at the time. That doesn't make it not nationalism, but at the time it was instituted I can understand where they were coming from.
Adding the "Under God" part and requiring it to be recited every morning before class wasn't instituted until 1954 during the Cold War era, when adults were worried that their children were commie spies. Their way of solving this was to shove Christianity and American Nationalism down the throats of everyone within earshot.
2,3,4. Via the Pledge's Wikipedia page:
In 1940, the Supreme Court, in Minersville School District v. Gobitis, ruled that students in public schools, including the respondents in that case—Jehovah's Witnesses who considered the flag salute to be idolatry—could be compelled to swear the Pledge. In 1943, in West Virginia State Board of Education v. Barnette, the Supreme Court reversed its decision. Justice Robert H. Jackson, writing for the 6 to 3 majority, went beyond simply ruling in the precise matter presented by the case to say that public school students are not required to say the Pledge on narrow grounds, and asserted that such ideological dogmata are antithetical to the principles of the country, concluding with:
If there is any fixed star in our constitutional constellation, it is that no official, high or petty, can prescribe what shall be orthodox in politics, nationalism, religion, or other matters of opinion or force citizens to confess by word or act their faith therein. If there are any circumstances which permit an exception, they do not now occur to us.
So as of current day, no, you cannot be compelled to stand and recite the Pledge. You WILL most likely receive nasty comments from your homeroom teacher, particularly if they are religious and/or older folks, and can be sent out of class to the principals office for basically any reason or no reason including this. It's against the law for the principal to leverage punishment against you for not reciting the pledge, but they can and will make your life very difficult if they feel like it without direct "punishment".
But in general, no, there is no legal punishment or precedent for someone who does not recite the pledge of allegiance. At worst, if you're accused of being a spy or of treason, it will be wielded as evidence that you are "un-American" and act as "proof" that you hate America. But it is not a punishable offense by itself.