解答：句子不能算错，但如果是针对学生而言，显然加上 of 更合适。

说明：out 原来只用作副词，但在现代英语中也用作介词，此用法主要见于非正式的美国英语中。如：

She leaned out the window. 她把身子探出窗外。

Our cat jumped out the window. 我们的猫从窗户里跳了出来。

He leaned out the window and waved. 他探身到窗外，挥手示意。

He sat for hours just gazing out the window. 他一连几个小时坐在那儿凝望着窗外。

I pushed aside the curtain and looked out the window. 我把窗帘拉到一边，向窗外望去。

He peered out the window to see who was coming. 他极目望向窗外，想看看谁会来。

She looked out the window and took note of the weather. 她望向窗外, 观察天气情况。

补充：《朗文当代英语词典英汉双解》第4版对 out 的介词用法有如下介绍：

out

prep [informal especially AmE]

1. from the inside to the outside of something – many teachers of British English consider it incorrect to use 'out' as a PREPOSITION 从…里面出去，离开…〔许多英国英语教师认为把 out 作为介词使用是不正确的〕:

Karen looked out the window at the back yard. 卡伦从窗口往外看后院。

Get out the car and push with the rest of us! 下车，和我们一起来推！